The secret boss Jevil from the first chapter was a pissing battle indeed. To access, you had to find three parts of a shattered key and unlock the jail. Then, your hourly trial of chaos bombs began, though with a goodbye treasure that was definitely worth it.
The second game chapter also hides a boss. And it’s under the thickest veil, so you can’t even guess who it will be nor talk to them. All you’re doing is collecting blue checkmarks as enigmatic Hecker tells you, waiting till the keygen drops in price, and wading in a forgotten basement for some old disk. And all of this for more suffering!