“Okay, I’m coming with you. Look, Mister Bright Eyes, if there’s some psycho running around hurting ponies in my home, I’m gonna help stop him. Got it?” 

Context: Dash told Twilight she was tagging along as they go to speak with Zecora, but Agent Bentgrass doesn't want her to come because he feels she will slow them down.

“What? I’m fine. That was one of the tricks we used to do in the ‘Bolts. The team would be flying at opposite ends of the stadium and I’d fake being knocked out. I’d fall, the team would race to try and catch me. They’d just miss me, everypony would be screaming. At the last second, I’d bounce of a cloud and roll to the ground, and the crowd would go insane! You know, you’d know this if you had gone to a few more of my shows like you said you would.” 

Context: Dash just performed a trick where it looked like she almost died, and Twilight was worried she was in danger.

“Uh, yeah! Do you have any idea who you’ve pissed off by kidnapping us? Well, first off, you have her brother, and my coltfriend. There’s a reason they call him Big Macintosh! He can buck a tree clear out of the ground, and when he gets here, he’s gonna break you in half!” 

Context: Dash and the other girls, minus Twilight, have been kidnapped by the killer. Dash is trying to stall so help can arrive, so she is giving a cocky speech to the killer about how badly he messed up by kidnapping them. Also, she finds this all hilarious, so "He's gonna break you in half," should be said through laughter.