I thought he was okay in Arrowverse, but wasn't as good as the first three series villains. I prefer The Suicide Squad version, mainly because Peter Capaldi has the perfect look for the Thinker and partially because I already liked Peter Capaldi from Doctor Who.
Also, my favourite non-speedster Flash villain has to be Rag Doll. Rag Doll's Arrowverse version is so freaky and captures the original character perfectly. Also a great casting choice too, since anyone else would break all their bones trying it.