Who beat the best version of Wlad?

I'd say Fury. Sure he was past his prime but the Joshua fight proves he was still capable of operating at a very high level even at that late stage of his career.

When he fought Brewster he'd only just started working with Steward he had't had time to really change much. Just look at how aggressive he was in that fight, that's not the Steward Wlad we saw in later years that dominated the division. Wlad threw 311 punches during just 5 rounds, that's almost as many as the threw over 12 rounds vs Haye. He became for better at pacing himself and slowing fights down later in his career.

 

Some respect

 

The correct answer is clearly Sanders. Sanders bombed Wlad out when he was at his offensive best and full of confidence.

Brewster beat an all-time low confidence Wlad who was still acclimating to and badly misusing the kronk heavy clinching style. Wlad gassed badly mostly because he kept needlessly expending energy pushing Brewster around the ring.

Fury beat a near 40 year old Wlad who had just gone life and death with Bryant Jennings.