The Syndicate

First there are some jumping robots that have too much life and are better off avoided, except they jump at random so you will take the risk to let they damage you. Then there are three flaming pillars that you need to freeze with perfect synchronization to pass through. You probably won't be damaged so this just makes you waste time. Then there is a life restorer that you don't actually need but is extremely hard to reach, so it will tempt you as you fail to jump to it. Then a section with a thousands small robots that are easy to kill but respawn like crazy. Then a section where you have to ride some floating green robots over a lava pool. But they move at random so you'll spend most of the time waiting for them to decide to go where you want. And praying they don't randomly decide to take you to the spikes in the ceiling. Then you gotta use the magnet beam to make some very precise jumps over two walls. Fail and you'll have to go back to regain ammo, which is easy, but takes at least 2 excruciating minutes of going back and forth the screens.

All of that to get to a boss, die in 10 seconds and have to redo it all again.