To be honest, I can't remember a less likable top 10 player. Tsitsipas is close, but he's not quite as bad as Zverev, imo - and doesn't beat up his girlfriends, afaik. Bernard Tomic had a similar kind of pouty entitlement, but was a much lesser player so is more pathetic than anything else. Fognini was a prick, but he wasn't an elite player. Soderling was a bit of a jackass, but Zverev's entitlement is more irritating. Kyrgios obviously comes to mind, but his antics are fun to watch, and he has a sense of humor. Similarly with Medvedev - he's at least funny. So Zverev takes the crown, at least among players of the last 10+ years.
Among legends, the classic is obviously Mac, but he could back it up with brilliance and I think most have grown to love him.
Serena Williams comes to mind, on the women's side. I'll never forget her trying to steal the 2017 US Open title away from Osaka with her primadonna whining. It was unbearable and made me lose a lot of respect for her. Novak in his early years with the shirt tearing, but he mostly grew out of it and was always so gracious in losing so I think all but the most butthurt Nadalites grew to respect him.