Listed as f(x) second main rapper after Amber. Sulli is actually ahead of Amber for me personally because ironically enough her soft sweet voice for whatever reason works wonders on top of the rough and rugged beats that f(x) is usually supplied with.
A few of my favorite Sulli rapping moments on f(x) songs are..
NU ABO. "Just argue 3 times. No hugs in the breakup. When you miss me and think of me. Just remember the couple rings". LOVE her delivery of these lines. Favorite part of the whole song.
GANGSTA BOY. She gets two parts at the very beginning of this song but its the very quick second part of the verse that is the most memorable when she playfully raps "When I caught sight of my Dads eyes. It was scarier". Her iconic facial expressions rapping this line during live performances gives it bonus points.
STEP. Very brief moment that most people wouldn't even think of but her delivery is so catchy. At the very end of the song she raps "go wherever my feet take me" she pauses then concludes with "I run whenever the wind blows". Perfect end to my favorite f(x) song of all time.
MILK. Krystal drops a rare rap line and immediately tags Sulli in as she so smoothly enters with a "Yeah. Yeah. I understand and accepted it. It's not that complicated cause it was always white". Sulli fucking kills it.
DRACULA. In what is probably my favorite Sulli moment in any f(x) song. Her jump onto the beat, with her bad ass delivery and insanely confident voice Sulli fucking MURDERS this entire track and steals the whole show from everyone involved when she raps "Dont be alone. Dont walk in the dark. The moment he opens his eyes. You better run run run run run run run run".
Anyone who said f(x) was better without Sulli is out of their damn mind.