I'd like to say Quasar because Protectors are assigned a specific universal menace (Thanos was for Captain Marvell, Melstrom was for Quasar), so seeing as Thanos is one universal menace and Quasar is an assigned Protector then they would stalemate...
BUT Thanos would likely mop the floor with him. Thanos simply has too much raw power for the bands to contain - Earth strongmen (Hulk, Thing, Colossus, Sasquatch... etc) all started pounding on a quantum shield to no avail then out of nowhere Thanos blasts right through.
Wendell's going down.