Drax the Destroyer.
 
~Rex

Silver Surfer? Thor?

I'd say either Adam Warlock or Silver Surfer, though Thanos was originally an iron man enemy

Drax was made to kill Thanos but seeing as he has already did that, he cant anymore. I'd sy Adam Warlock

If Thanos is truly a carbon copy of Darkseid, then who is his constant deterrent who can stand up to him and not get their ass handed to them?

Thanos is a carbon copy of Darkseid, PC-Darkseid. Only he's a suped-up Villain Sue. Anyway, he doesn't have a "Superman", Drax is his Orion, who is the true enemy of Darkseid, not Supes. 

^ that's right.... Surfer is but almost never wins. I've been told that Superman also had a long history of defeats by Darksied though.... Warlock is the only one who seems to know how to beat Thanos but he does it more by his ability to sense what Thanos is doing and plan ahead for it rather than winning one on one or by pure powers. There is a looooong list of heroes and villains alike whom try to stop him on a regular basis.

Captain Marvel was initially Thanos's arch-nemesis. Since Marvel's dead, that title has belonged to Adam Warlock.

None of the Marvel heroes are strong as Superman .

@shaokahn: What about Hulk or the Surfer? Thor?

Captain Marvel or Adam Warlock

@vampireselektor: Surfer is above superman but Hulk and Thor doesn't hold a candle to Superman .

Mar-Vell until he died and Adam Warlock afterwards. Drax is an important enemy from a life vs. death standpoint but not really his arch-nemesis.

As stated above currently its Adam Warlock but there more frenemies right now. I think they have been angling Star Lord as Thanos nemesis. with Thanos Imperative and recently in his own series.

Thor

Himself and only himself.