When look at Alberto Del Rio's time in WWE, I can't exactly say that I feel sorry for the guy because from my perspective, he's got got a whole lot to complain about. Inside the ring, I really enjoyed Del Rio. I thought he was a really good technician who could brawl when called for and could do it easily. I mean, the guy's about 6'4" or 6'5" and weighs about 235, 240 lbs. so he's not really someone that can do all the various flips & flops and suicide dive variations that we've come to expect from most Hispanic wrestlers so that did make him stand out a bit.
On the mic, he got pretty old after a few months because all his promos were essentially the same as he'd talk about "destiny" or calling someone a "perro" or what have you. His gimmick with Ricardo Rodriquez was fun and even though it was essentially a cross between JBL and Ted DiBiase's Million Dollar Man gimmick, it was still enjoyable overall.
During his first run, Del Rio was a 4 time World Champion, won the largest Royal Rumble match in history and was Mr. MITB. He was consistently in a headlining position even though about halfway or so through his run, I'd say, a lot of people just didn't really buy into him all that much as a main eventer. During his second run, I still can't say I was overly sympathetic because here's a guy that for about 1 year had a downside guarantee of well over $1 million and ultimately left because he was pissed about not being in the main event spot.
If Del Rio has hard feelings towards WWE, then I'm of the opinion that it's due to his own making. When he was released the first time, he assaulted another company employee. I forget his name and what he did exactly, but the guy wasn't a wrestler and he did so because Del Rio said he made a racist comment/joke towards him; Del Rio is the only one who heard this, so WWE's hands were tied. If true, then the guy deserved to get the taste slapped out of his mouth but at the same time, in the real world, you can't just go around physically assaulting people and companies can't permit it to happen. In the United States, you can sue over damn near anything in the first place so WWE either takes action or they get sued by this guy who got pasted. They eventually did fire this guy, as I remember, after investigating him as it turns out that he had a history of making such comments and jokes but it's not like WWE could just fire the guy right then and there without finding out all this.
I've read that Del Rio was "promised" a main event run but other guys in the past have made similar claims. It sucks sometimes, but pro wrestling can be a fluid business where you sometimes have to go with the flow. In Del Rio's case, in my opinion, he wasn't all that interesting as a main eventer and he'd had lots of opportunity before and I don't think I was the only one who had that opinion based on fan response. The whole Mexican-America thing felt awkward from the beginning, I think WWE sensed that but kept it going for a bit in the hopes that he and Colter would find their groove, but it just felt strange; doubtless it was one of those ideas that seemed good on paper but didn't pan out in execution. Also, as I mentioned, Del Rio reportedly had a downside guarantee of well over $1 million and, to top things off, he became involved with this cute, British 22 year old, at the time, who seems to think the sun rises and sets on him.
So yeah, all in all, I think Del Rio's issues with WWE are more along the lines of his ego being bruised than anything else because he had a lot of high profile things going on, met his current wife and made a shitload of money in the process. I'm not gonna be shedding any tears for the guy, I'll tell you that.