I'm talking about the 3rd ending where you fight Time Devourer with only Serge.
I kept on attacking and it just didn't seems to die, I used a calculator and the damage I did was much more than 10000 and it still there! Does the Time Devourer's HP is 10000 or is it more?

i dont think you can kill time devourer with attacks only..unless you want to kill princess schylla as well..

no, I guess she's talking about the "Developers Room" ending, to get it you have to defeat Time Devourer with Serge alone at the very start of New Game+..

anyway, you should try it during your 3rd playthru honestly.. he's still too strong to beat during the second playthru with Serge alone. I dunno his exact Hp.

You can definitely destroy him with just Serge. It'll likely take a while, though.

Also, if you have an anti-freeze accessory, equip it. If his IceBlast element freezes you, you're done.

The Developer's Room ending is like the most boring one of all. ZzZ... It was so hard beating that a-hole with only Serge to get such a lame ending where nothing happens. Grr.

I thought it was the most fun.