The Panthers were the best tank of WWII. T-34's were good (better than Shermans) but could not match 1 on 1 with a Panther (or Tiger) in any way (armor, firepower, etc). However - the Russians produced them in such numbers and deployed them in mass wave attacks that even losing the first couple (or more) to a Panther - they would get close enough and eventually destroy the German tanks...
When they ran.