Bad guys can't be awesome? Allow me to introduce you to Mihawk.
When was it ever confirmed that Mihawk was a bad guy?
If anything, Mihawk's been very tolerant of that green haired upstart who had the nerve to interrupt him during his fight with Don Krieg. A true bad guy in the same situation would have split Zoro into three pieces, said something rude about "dreams" to Luffy and sailed off into the sunset. By doing what he did, Mihawk actually helped Zoro (ok – I know that sounds bizarre, but just keep reading ...).
We know from what Zoro told Sanji that he (Zoro) had been recklessly "throwing his life away" in persuit of his dream. So we can infer from it that Zoro wasn't focusing realistically on his goal, so much as just wandering around impatiently, hoping for the day when he'd (literally) cross paths with Mihawk. And that's exactly what happened at Baratie : Zoro had no idea that Mihawk would be there, and because of that, Zoro was unprepared for the fight. But since he already considered himself "dead" at that point, he had no problem with challenging Mihawk anyways -- because dying while fighting Mihawk would be better than dying fighting some nameless East Blue pirate.
Mihawk -- and basically everyone else (even Johnny and Yosaku, which is really saying something!) -- could tell right away that Zoro would not be able to defeat Mihawk, but there was no easy way to get Zoro to back down from the fight, because to do so would be to lose his pride (and we all know from DBF that Zoro would rather "die" than lose his pride). So the fight had to continue until the point at which Zoro could no longer fight, because as long as he could still fight, he would ... and if he kept fighting for too long, he'd die.
So Mihawk's decision to wound Zoro was actually quite strategic -- not only was it a fine example of top-tier swordmanship (and one that would stay with Zoro forever in the form of a scar across his chest), but it was also an effective way to stop Zoro from fighting till his death.
Still think Mihawk is a bad guy?
After Mihawk wounded Zoro, he could have simply said "take that, stupid brat!" and sailed off into the sunset, but instead, he stuck around long enough to salvage Zoro's pride -- by speaking respectfully to him in front of all the on-lookers (Zeff : "why would Mihawk say something like that ...?") -- and then, as if that wasn't enough, by giving Zoro a little pep talk/ "To Do list", which was as follows:
(1) "know yourself ..."
In other words, stop trying to live someone else's life and live your own instead. (Or, to be blunt about it : stop trying to be Kuina, start trying to be Zoro)
(2) "know the world ..."
In other words, East Blue is not the planet, it's only one small part of it, and if you judge everything by East Blue standards, you won't survive in the places that don't resemble it.
(3) "become stronger ..."
Mental, emotional, spiritual, physical, etc ... : because you can't be considered "the strongest" until you've got strength in several areas, as the New World pirates and Shichibukai do.
(4) "use your will to surpass me ..."
This is basically Mihawk's way of saying "stop being so damn reckless and stop being such a damn slacker -- take logical steps towards your goal instead of passively waiting for your goal to find you".
So what has Zoro been doing since then?
Training; taking an active role among the Mugiwara (when he's not sleeping, that is ...); fighting battles when necessary -- avoiding them when not; thinking about difficult things (like Usopp's return to the crew) that others hadn't always given serious thought to; not letting "even death himself" take his life; focusing on his goal in a pro-active way.
So no, Mihawk is not a bad guy.
Mihawk is a mentor.