I started following club football regularly around 2004. His first Chelsea team was nearly unbeatable - impenetrable defense/goalie, powerful midfielders like Essien, Makelele, a bit of flair in the likes of Robben, Cole and obviously Drogba and Lampard to score the goals. They used Abramovich's money to create an incredibly strong first XI as well as an equally strong bench. This was something other top English clubs simply couldn't afford back then. At times, they seemed to sign players just so that they couldn't join their rivals. I remember the hype for the Barcelona-Chelsea CL tie in 2006, it was pretty clear that these were the two strongest club teams in the world, with AC Milan close behind. So what does Mourinho do? Does he attack Barcelona at home and try to put them under pressure? No, he puts out an absolute potato-patch of a pitch to ruin their passing game, tries to kick them off the park, still gets destroyed by Ronaldinho/Messi/Eto'o, and then proceeds to blame Messi for getting maimed by Del Horno. Ever since then, I've hated the guy.
He is the poster-boy for reactive football. He openly scoffs at the idea of instilling an identifiable style of play, or developing attacking patterns that get the most of creative technical players. When he faces technically gifted teams with comparable resources, his entire gameplan has always revolved around sucking them into errors, or overcommitting while attacking, and then hitting them on the counter-attack. He tries to ruin the flow of games against good teams by niggling fouls, diving, playing for set-pieces etc. Since he's always had huge resources everywhere, you can get away with this "tactical genius" approach against the few top teams you play every year, and smash mediocre opposition with Ronaldo, Drogba, Hazard etc. Obviously it's worked in the past against naive managers like Wenger and Pellegrini. Not so much against Guardiola, Klopp etc. Being found out big-time now. More managers have wised up over the years, and he simply hasn't adapted. And he doesn't have the fall-back of having a clear, identifiable "Plan A" style that he can coach.
But my dislike of him is not even so much the ugly tactics. He's an absolute arsehole of a human. Everyone knows about the numerous clashes he's had with various referees, managers, players, owners, medical staff, mostly provoked by his own ego, where he's belittled, mocked and abused others without provocation, made up conspiracy theories, intimidated people, you name it. He's kicked so, so many people on the way up. They will enjoy kicking him twice as hard on the way down. He deserves every bit of it. I hope he fails hard and gets sacked by Christmas like he did at Chelsea last year.