* DemonicSpiders: Literally with the Tanks and the not as large black and white striped warrior spiders, they are probably the main cause for controller hurling frustration. You at least get some forewarning of them, but the first time you encounter either will definitely result in a loss. Tanks move through walls of towers without slowing down, its impossible for a tower to survive a tank. The black and white spiders will destroy any towers outside of a repair tower's range, and in enough numbers the repair tower won't make a difference anyway.
* GameBreaker:
** A necessary one at that, the Amp tower boosts the range and damage/heal of all towers in range, the damage buff also stacks from multiple Amp towers, but this will ensure you barely survive as opposed to failing horribly.
** The AntiAir tower is a lesser gamebreaker, when fully upgraded and paired with a maximised Amp tower, it has a ridiculous range compared to any other tower, being able to almost cover the entire map. With 7 of these paired to an Amp tower all but boss fliers will die shortly seconds after spawning.
* GoddamnBats: All fliers to an extent, they draw your towers' attention away from the harder to kill ground bugs. The purple/blue worms and the large spider which births a ton of smaller ones on death are also pretty good examples.