For killing the Atomic Leviathan at the end of the game. My build for this was atomic body (for the laser beam), shadow teeth (for the health on bite bonus) and bone for the rest, mostly for the extra damage resistance. Equip mods based around resistance, the health regen and the sonar that weakens all around you. Charge the laser and shoot, when the other bosses are summoned largely do the same. This is where the shadow teeth can help as you can get health back by just chomping anything. The Leviathans armour recharged pretty quickly, don't be surprised if you have it on a slither of health but full armour. Just knock the armour off with teeth and laser and you're good. Once the Leviathan is dead any surviving other bosses will disappear.