My opinion on Cena has fluctuated so much throughout the years. When he was a new guy on Smackdown, I was just starting middle school, so being that age, I ate up everything. I really started cheering for him during his feud with Carlito, so that's probably a defining moment for me. The next is a more iconic one: Cena lifting up Big Show at WrestleMania XX. I saw that WrestleMania as a real changing of the guard, and a vision of the future, and Cena certainly showed that he had the strength and charisma to do it. Shortly after that, I got tired of Cena, and became a big hater for years and years. The PG Era only exacerbated the hate.
The Cena hate remained until WrestleMania XXVI. While the night was overshadowed by HBK/Taker II, I remember Cena/Batista almost as vividly. I was pretty underwhelmed when I realized that Cena/Batista was up next, and it was one of the last matches. "Oh, goodie. Time to watch Cena get beat down for 10 minutes, then come back and win 'out of nowhere.'" But I was blown away by the match. Cena and Batista put on a clinic in a very underrated match. I was actually on the edge of my seat. Two spots stand out in my mind: the (somewhat botched, if I remember correctly, but still impressive) top rope jump by Cena into the Spinebuster by Batista, and the big Attitude Adjustment to end the match. Those moments stick with me as really impressive, defining moments, and show that Cena can win over even the biggest skeptics when he really tries.
The most iconic thing for me, though, is what he did after the match. This picture says it all.
This really showed me that Cena realized he had detractors, and he didn't let it bother him. The picture just speaks for itself. The haters are always gonna hate, but Cena will continue doing what he does best: entertain. That image will always stick in my mind when I think of Cena, and is one of the most defining images of his career.