If you camp out at an ant hill, such as the one in the tutorial, and you have the energy bolt powerup, you can slaughter ants and build up a charge that can last several minutes. From there, you can run over to Frogatto Grotto, teleport to Milgram’s castle, and easily overpower him since your energy attack is more powerful than his.
This does take time – more time than it would take to beat him legitimately in the first place. It still seems a bit powerful, though, especially since it’s the only one of the three powerups you can get indefinite use from: the reflexes one won’t last much longer than normal because it runs out faster than new enemies can spawn, and killing your enemies the normal way probably takes too long for you to be able to build up an invincibility charge.
Just to let y’all know.