Thor has plenty of counters. I have 2 creatures above 145 speed (Magna and Nemys), plus SIA monorhino. Others have Draco, Erlyko, Erlidom, Monolometro, all those creatures can counter Thor. I’m in shores and believe me, I’m usually glad when opponent has a Thor, it’s usually an easy kill (unless I’m unlucky enough to not have any of the counters).
(EDIT, important to say, I have never spent on game. If you play enough and collect all your drops, daily inc, strike towers, you can have more than enough boosts by now. I used to complain about boosts, but now, without spending, I have enough to fully boost my entire team, just by getting all the free ones the game offers)