Some of these cases may be a little out of date but I got a few cases for gen 8 (and by that I mean pretty much all of them)
. Gastrodon is 29th in OU, but 83rd in UU and 32nd in RU
. Nidoking is 46th in OU, but 57th in UU
. Cloyster is 56th in OU, but 66th in UU
. Kingdra is 67th in OU, but...