I've always felt that Max was the most abusive. Not in his relationship with Liz, but with Isabel and Michael.
There are two types mainly portrayed in the show. Physical and Verbal.
Physically...I always thought Max was the most abusive. I don't recall Michael every throwing the first punch. He might get in your face and argue, but he never got physical. Max on three occasions (not including season 3) hit Michael first and normally considering the characters personality, it would seem Michael would be the one to throw the first punch and not Max (but then again, you have take into account Micheal's abusive foster care past...and then take into account that Max knows about Micheal's past and still hits him)
You can't really count when Max became Clayton. Max wasn't fully Max in that episode and you can blame him for how violent he got there. Same with Michael when he became King...he wasn't fully the Michael we know...and you can't blame him for getting violent in there.
As far as the scene where Michael pushes Maria out of the car...it was just that...albeit it was rough...and same with Max when he was Clayton...(and yes you can argue that it was Clayton and not Max) but wasn't there a scene in season 2 in the hallway...where Liz was talking to some techi guy about getting help with hacking into Alex's computer to find out who killed Alex...and Max roughly grabbed Liz's hand. They were both rough here.
Verbally...I don't think there was any abuse between the couples at all. But I do see some between Max/Michael/Isabel.
Relationship wise..I don't think Michael was ever abusive to Maria...I think they're just both high maintenance people that liked to argue and bicker back and forth...I don't really recall Michael ever being abusive towards Maria.
Everyone argues that Maria broke up with Michael when Michael stayed for Maria. What so automatically Maria is suppose to not have a life anymore just because Michael stayed for her? She said it herself when she broke up with Michael...she was breaking up with him because she loved him too much, more than he could possibly know. She broke up with him because she knew that she was loosing herself and if she didn't try to figure things out for herself, it would only hurt Michael later on if they had stayed together and not worked out whatever issues they had.
And the way I interpreted the last two episodes, they were working their way towards getting back together. In Four Aliens And A Baby, Maria slept spooned against Michael...that's a little intimate for someone that is suppose to be your ex-boyfriend right? And even in the last episode, before Liz got her visions, didn't Maria ask Liz jokingly if she could predict what would happen between her and Michael? She was obviously already thinking about her and Micheal's relationship and getting back together with him on some level...so much so that Michael went with her to Madam Vivians (Maria already made the appointment before they found out about Liz's vision)...again they were trying to work their issues out the way I see it...the only problem was that they ran out of time when Graduation happened and Maria had to make a choice...and she picked Michael. To say that Maria left because she didn't want to be left behind...is crap, she was willing to walk away before...not just from Michael...but even from Liz and the rest of the gang...she was going to NY, she went to NY. Why didn't she just stay there? She was stronger than all the other characters in knowing that there is a time to walk away and time to stay. In the end she had to make a choice and she choose Michael for a very obvious reason...she loved him.
Everyone forgets about Isabel wanting to leave everyone and go to college when she graduated early...AND SHE'S A FREAKING ALIEN.
Or Max...thinking about leaving behind Liz/Michael/Isabel when he went to the NY summit? No one remembers that. Or what about when he went to looking for Kal and the ship, heck he would have boarded right there and then with prob just a phone call goodbye and left everyone without a thought...but again no one thinks about that.
Or Michael wanting to leave everyone behind in Independence Day. Why is it okay for the aliens to walk away, but for the humans, its looked at such a huge betrayal?
To call Maria selfish for breaking up with Michael because she was loosing herself is crap. She doesn't owe Michael her life and neither does Liz...again didn't Liz leave for Vermont specifically to get away FROM Max? Shouldn't it be selfish of her to do that? The only difference between Liz and Maria in those two scenes is how the pain for each character was portrayed. Liz was hurting externally...we could see her pain (with her powers and stuff) but with Maria it was all internal, kept hidden and we couldn't see it.