The way i beat the final boss was to take dynamite, shield, heal, and stun.
Shield the melee and try to keep him alive as long as possible b/c the stun is useful, but he's going to die first.
Next just use dynamite whenever you can and shield whoever is lowest until your heal is up.
I had my group fully upgraded so i strongly suggest doing the same if you somehow got to 26 without doing it already.
Anyone else's keys sticking? It didn't start until i started insane mode and I've played another -arrow keys controls your character- game and they didn't stick...
i beat the whole game and didn't get a single achievement.... then i reloaded the screen and it brought up level one, so that's a serious glitch you need to fix.
you just have to pause the tank just as the tower starts to blink.... then your tank doesn't flip. But word of advice, if you upgrade to a full 25 health tank, upgrade the tires to or it is going to get stuck...
 "Ninja and Blind Girl 2"){kind=icon}
 "One and One Story"){kind=icon}
 "Focus"){kind=icon}
 "Bunny Invasion 2"){kind=icon}
 "Flaming Zombooka 2"){kind=icon}
 "Thanks Tanks!"){kind=icon}
 "William and Sly"){kind=icon}