Searched for this fight on here, but found none except in battles with a lot more other characters. So, in this battle, It's Ultron vs Thanos.
Thanos in this battle has no prep, but is aware of who Ultron is, and he has his standard Force field thing with him but does not have access to other technology in this battle. Ultron however has 3 days prep and is on a mission to eliminate Thanos by any means necessary. Thanos only has 10 minutes before he knows Ultron is coming his way. So who wins this battle?