Establishing Character Moment: Professional Wrestling
The debut of Kharma (the former Awesome Kong) in WWE. While the vignettes that had been airing painted her as no one to be trifled with, her first actual appearance came at Extreme Rules 2011, where she came out after Michelle McCool lost a Loser Leaves Town match. She took her time getting to the ring and stalked an absolutely terrified McCool (a multiple time Women's/Diva's champion, mind you) for a good two minutes before getting in the ring and completely destroying her with an Implant Buster, then cackled insanely while the rest of the WWE Divas division looked on in horror from the locker room, knowing they are monumentally screwed.
"Stone Cold" Steve Austin when he became King of the Ring 1996 "You sit there and you thump your Bible, and you say your prayers, and it didn't get you anywhere! Talk about your psalms, talk about John 3:16...Austin 3:16 says I just whipped your ass!"
When he first became Stone Cold, he refused to wrestle a jobber and lost by forfeit. Then he came back and beat up the guy anyway.
John Cena debuted in 2002 as a generic wrestler wearing generic gear coming to the ring to generic music so bland the audience likely tuned it out. But the impression of a lifelong midcarder or one destined to be future endeavored vanished when he took the fight to Kurt Angle, countering Angle's finishing slam and ankle lock during their match and in general showing the attitude of a man who would never back down to any threat.
Six months into Cena's WWE career, he was on the road to being lost in the shuffle until a Halloween episode of Smackdown, where he appeared dressed as Vanilla Ice, cutting promos in freestyle rap. He hasn't looked back since.