Personally, I think he made a bad choice and should have stayed with Bellator where he could cherry pick easier competition.
Who do you see him defeating in his UFC return?
Fuck off:
Mitrione
Mir
Nog
Werdum
Arlovski
Browne
Struve
Schaub 
BeatonHauff - Possibly Shawn Jordan, maybe schaub now.lol came here to say Shawn Jordan
Dom Hemingway - Fuck off:Add Nelson
Mitrione
Mir
Nog
Werdum
Arlovski
Browne
Struve
Schaub
Anyone he kicks in the head.
Struve, Nog and Mir. That's it, sadly.
Actually, maybe Overeem.
If he gets guys on the right night, its possible he can beat them. I guess we'll see what happens. Mirko's always been about the promise of something better than the actual results he got. From not winning a legit K-1 GP to not beating Fedor to not performing in the UFC, he's pretty much always been consistent at being inconsistent.
Cro Cop beats himself in the cage...everytime.
Crocop would good be good fight for when lesnar comes back
i dont know who he can beat but there are many fun fights to be had and many cards to be filled.
My first thought when I heard he may come back was "awe shit who's record are they padding". I don't want to see crocop get beat so I hope they put him up against another fellow vet on his way out and not no new comer who the UFC is wanting to build up.
CroCop vs Arlovski, for old times' sake
Big Nog for the elderly championship.
he's going to need upsets to beat the top 15.
A good question to ask with hindsight is, who was Cro Cop's best UFC win? Pat Barry? Eddie Sanchez?
Cro Cop v Gonzaga 2
I_Destroy_U_Bro - Cro Cop v Gonzaga 2Ding ding ding!
I think rematch with Big Nog and Mir are both winnable fights. I don't see him doing well against boxers like AA or Stipe as it would likely be akin to his JDS fight. Barnett is another intriguing matchup. So there are good fights for him to be made as long as the UFC sees to it.
Lets not forget Struve. That might be the perfect return fight for him and very winnable imo