Don't mess with Marky Mark
At this point, the movie pivots quite dramatically. You can blame the beginning of this shift on Nice Gary, Reese’s L.L.Bean fleece-wearing friend, who has the audacity to give her a hug goodbye at school. Marky sees this, and beats the shit out of him -- and hits Reese, too, and now she's got a black eye and is somewhat pissed at Marky Mark, who genuinely can't understand why she's upset that he nearly stomped her friend to death and bruised her face.
One of the reasons Mark Wahlberg is so good in this movie (and I mean that sincerely -- he's creepily perfect), is because you believe that this is exactly how Mark Wahlberg acted in real life when he was 18. Remember that Wahlberg's teen years involved a gang, an attempted-murder charge, and a felony assault conviction that he's still trying to get overturned in Massachusetts. Everything Wahlberg says in the film sounds authentic, and that makes it even more terrifying.
Take, for instance, another iconic scene, which takes place after Dr. Gil calls his CSI buddies and they check up on Mark Squared and realize he's been in jail for most of his life. Both Mark and Gil are in their old, refurbished cool cars and get out to confront each other. Gil is like, "You can't see my daughter anymore," and here is exactly what happens next:
Marky Mark: You know, Steve, you're really not a faggot.
CSI Gil: ... What?
MM: No, I'm serious. You seem like a pretty solid guy; you should lighten up on yourself.
CSI: We're not talkin' about me, we're talkin'...
MM: Yes, we are. That's what this whole thing's about, Steve. Your inadequacies. Your fears.
CSI: You just wait a minute...
MM: Listen to me. See, I'm hip to your problems. All of 'em. I know you abandoned Nicole when she needed you most... 'cause I licked her sweet tears. I know about things comin' apart at work. Maybe you fuckin' lost it in that department. I also know you ain't keepin' up, so to speak, your end of the bargain with the missus. 'Cause if you were, she wouldn't be all over my stick. Relax, Steve. We're friends. We're practically family.
CSI: I want you to understand somethin', pal. If you don't disappear from my family's life, I'm gonna rip your balls off and shove 'em so far up your ass they'll come out your fuckin' mouth! You got that, my friend?
The way Wahlberg delivers those lines, it’s just... holy shit, I kind of think he might’ve cribbed it from a toast he gave at one of his buddies' parole parties. CSI Gil, to be fair, gives it his all with his last line, and I think the director wants you to feel like it was nearly a draw, but it isn't a draw. Marky Mark puts CSI Gil in a pot with cream, clams, potatoes, onions, and at least one bay leaf, and chowders the shit out of him. And as the oyster crackers on top, this is the exact point when Marky does that hitting-himself thing Matty McConaughey also does in Wolf of Wall Street, but harder, then tells Reese her pops hit him! And who even knows what he’s doing with the clocks!