Nothing, block them and move on...
What do you guys do against cheaters ?

Some forms of posting an accusation of cheating could get you warned or banned. Best to leave determination of actual cheating to Chess.com and staff.

No. report cheating to staff directly- do not post accusations Anywhere, or you might get in trouble yourself.
that is chess.com policy.
and that is why I'm "in before the Lock!"
you cannot talk about cheating on the forums. report to staff, block, and move on!

@thegreat_patzer is correct: Report suspected cheating to the Support team via Help -> Contact or the direct link https://support.chess.com/customer/portal/emails/new
Definitely do NOT post accusations in the public forums or on their user profile: @smokering26 is incorrect with this suggestion.
The Cheating Discussion forum will help you understand how you can't tell whether someone is cheating from just two games - don't post speculation about the how or why of cheating in the public forums.
Locking.
Hi everyone !
I just got sweeped in 2 games in a very fancy way by a rather low rated player ( 1170). So I decided to put them in my engine to see what's going on. Guess what ? My opponent cheated on EVERY move.
If you find a cheater do you tell him to the mods or only block him and let it go ?