Sudden Death Blitz sets itself apart from the other Blitz modes in that there is no round limit. You simply go until the moneyball is destroyed. PitGirl also is universally proud of your performance each time, whereas she shakes her head in disappointment when the moneyball is destroyed in other modes. Bots will increase in strength and speed up to Round 60. Also after Round 60, Bullseye simply stops making appearances, perhaps because he becomes almost entirely unnecessary.
RockIt and ShaveIce turrets should provide the primary strategy in this mode. Long Shots will work in the corners, the rear with few players, and possibly the rear money ball nub. Initially, you should focus on getting rockets at the frontal exterior nubs. Once those are at level 3, you can effectively ignore the front. If playing with a Support, a Firebase placed on the small platform way in front will be invaluable in furthering your frontal defense while also eliminating troublesome Gap Shots instantly. Within the interior, you'll want ShaveIce turrets at the center of the front door and the centers of both sides. You can take your time making those, but you will absolutely need the time they give you at later levels. Eventually the bots will be so fast that you just have to slow them down. Enhance only the most relevant skills at first so that you have the most money to devote to turret construction. For some time, you'll want to use juice and taunt to raise more funds for your turrets (you shouldn't really need juice for a long time).
Passing level 10, it's important that you get RockIts placed at all spawn points. Although only Slim bots will come out initially, even they need to be addressed. The rear nubs should get rockets for 3-4 players, longshots for 1-2. You should also be very aware of your capability of dealing with Jackbot XL bots. You need to know when to simply engage them yourself or hit the Annihilator. In question there is whether you will need to rebuild turrets if you don't hit it. Basically, hit it if the number of Jackbots is greater than the number of players. Jackbots will come out at multiples of 10 for a while, so you can predict when you should be ready. Also, you may want to wait until the second wave of Jackbots comes out to maximize the Annihilator's effectiveness. If things get to be too troublesome for you, such as Gremlin and Bouncer bots working together, Ejectors can be very useful at minimal cost.
Passing level 50, you should have turrets all around doing the majority of the work. However, it is vital that everybody involved is familiar with the bot patterns and has specific points of defense they can take. The game doesn't improve at all beyond this point, so it will come down to how consistently you can keep to your routine. Juice stations are available should you need them, since money will become largely irrelevant. Black Jack bots actually become even bigger threats than Jackbots, because the Blackjacks are what will be hitting the moneyball. Your plan of attack will depend largely on the number of players and what classes you're using. If Jackbots get too close, they're likely to get a quick shot at the money ball to destroy the shield. However, because the turrets will tend to stay locked onto the Jackbot, they won't be stopping the advance of Blackjacks. If you can pass level 200, you pretty much have a solid defense going that could theoretically go forever.
The two best types to use in a solo attempt are the Support and the Assassin.
The Support is a strong class for a solo run. With so many Turret Nubs, they will become his weapons. Focus on the Hack and Firebase skills while building Turrets. Put the Firebase way up front, as described earlier, as Gap Shots will only come from the front. (It may or may not be relevant that the Gapshots seem to specifically come from the left front). Without them, Bots can only attack your turrets directly, leaving the Jackbots their biggest threat. From there, build, upgrade, heal, and Hack every Turret nub you can reach and afford. Start in the early rounds with the RockIts toward the front door, but hack the Firebase so they take most of the kills (kills by your Firebase count as yours; kills by turrets don't). Add the side coverage by Round 11 and the rear by round 21. Then build in from there. Jackbots will be your biggest issue, especially once Round 50 begins and they may Jackbots spawn like mad. Watch their entries and focus your healing efforts on those Turrets. Once you've got a good start on the base, you can stop hacking the firebase. The rockets will be more effective than the needles your firebase shoots, and money will flow naturally with each round.Jackbots will be what drives the entirety of the strategy. The rockets unhacked will just barely keep the sides under control, but that won't help anything once Jackbots appear. The turrets that look out through the gates will have the most firing time on enemy targets before they reach the moneyball. As an added bonus, they'll be more likely to keep firing on Blackjacks instead of the Jackbots. You'll have to put all your personal efforts toward destroying the Jackbots, so you'll need to rely on the turrets to handle the Blackjacks. If it helps, hack the turrets in a circular rotation so you don't lose track of what to hack next. Churros will be helpful to make sure you can keep these 4 turrets handled consistently, but if Jackbots come out too much, know when it's right to skip hacking a front turret so you can get to the internal turrets.
The Jackbots are going to be your only real hurdle; everything else can be handled easily. It is perfectly acceptable to use the Annihilator at the first sign of Jackbots if you're able to reach it within no more than 2 seconds (read: you're on the upper walkways, either at the Annihilator or near a jump pad to take you there). Swarms of Jackbots will be extremely difficult to control and you don't have the speed to reach it from the ground when you need it. The concern is more about reducing the number of Jackbots, not eliminating them all. For normal encounters, you should have juice ready at all times if possible. Your goal with encountering Jackbots will be to keep them from passing the front gate. Get right into the front field and force the Jackbots to slam the ground. If the Jackbots get into the internal area, they will fire 2 rockets at the moneyball, and the hit that drops the shields also damages the moneyball. You can't afford any damage at all. Make sure they want to fire at you and nothing else. While stalling them, use your hurt gun for damage. The shotgun is more damaging at close range, you need to be in full control of both Jackbots all the way. It will also help you to stay alive through all this. DO NOT EVER RUN TO THE ANNIHILATOR WHILE ENGAGED WITH JACKBOTS! Even if you have 3+ consecutive waves of Jackbots approaching, the Jackbots will do more damage to the moneyball while you're away than if you stayed to confront them. Keep them as far in front as you can, let the rockets do the work.
This editor used this strategy to reach round 2262. Aside from an honest death from Buzzers & Jackbots together, the moneyball only ever dropped when I failed to avoid slams, and was therefore not able to stop them from advancing.
The Assassin brings speed and bot-killing efficiency to the game. This means she can cover the field very rapidly (allowing her to reach lots of Turret Nubs quickly) and respond quickly to changing Spawns. Build the Assassin and Dash skills quickly, then focus on Turrets. Her sword lunge takes Slims, Gremlins, and Scramblers in one slash. Black Jacks and Gap Shots can be handled with a quick follow-through slash, and Bouncers can be grappled. You can handle a Jackbot or two in early rounds, but later rounds (and especially after Round 60) should have you fall back to using the Turrets and (if available) the Annihilator, as Jackbots will be too numerous and will start covering each other.
It should be noted that, while there will be a time when bots approach from the rear, that time will end in 2-player games. For that reason, placing Long Shot turrets at all rear positions is preferable. Rockets are worthless if they have no targets.
Support + AssassinEdit
The Assassin is going to have to get up close and use her sword a lot. You don't necessarily need the sword immediately, but you will want sword and Smoke Bomb a priority (for the defense increase). It is recommended you have endorsements for speed and rate of fire so that, in the late stages of the game, you will be able to quickly hit bots around the field. Unless you can actively track Buzzers, keep yourself cloaked when they are present. For the final routine, take up position at one side entrance, destroy the bots there and quickly make your way to the other side. Once you get the bots there, smoke bomb any bots that managed to get in from the center.
Support is going to have a somewhat tougher time being effective, but he's still very valuable. Until you get in the final set, you'll want your firebase up front on the little platform purely to take out Gap Shots (hitting other things is a nice side benefit). Hacking ShaveIce turrets can be surprisingly effective against the already slow bots, reducing them to a crawl. Make sure you keep your distance away from Scramblers and hit them with just the tip of your Heal/Hurt gun. Your grab will instantly kill any Blackjack at any level, and you will eventually want to keep it out to get Blackjacks. But if you do grab a blackjack with your shotgun, the hack skill will be still when you are grabbing it, so don't use it too often. Late in the game, you'll probably want the firebase back in the center, since bots won't stay in the spawn area long and Gap Shots will rarely appear. Keep your hacks focused on the rockets in the center. The Assassin will be able to do a lot of the work on bots, leaving you to keep your turrets hacked and healthy. Still, don't let your Air Strike skill go to waste. It won't kill the Blackjacks, but it will definitely help significantly.
Ironically, it will fall to the Support to grab the Annihilator. Support can't do much to destroy the Blackjacks, but the Assassin will be busy dealing with both sides in that regard.
Assassin + Support + Gunner + AssaultEdit
This is an ideal group for getting high rounds. The Assassin can easily take out BlackJacks while the Gunner provides superior firepower with the Minigun. The Assault can also provide some firepower and can even use his Bomb to fend off some BlackJacks. The Support can use his Firebase and even his Air Strikes to take down some BlackJacks and other special Bots.
With the Assassin on the offensive, it allows the rest of the team to focus on other areas, which helps keep the Bots away from the Moneyball. While the Support is hardly on the offensive, he contributes by hacking turrets and healing the other teammates. The Gunner can just unload the Minigun on other Bots while constructing a turret or two between every other round. The Assault is a surprisingly great teammate as he contributes to the Gunner's firepower and the Assassin's offensive strategy, making the chore of destroying Bots easy.