quentin grimes as a freshman 49% TS. second year in the league - 62% TS. that's basically the first dude i remembered. took me about 30 seconds to find that.
(edit) second guy i looked at - Tyrese Maxey - 53% TS, second year in the league 59% TS, third year 61% TS.
Cam Reddish 49% TS, third year in the leauge 56% TS - that isn't a great number (though it's fine), but it's a huge improvement. George improves that much, he's in the 58-59% range.
immanuel quickly 54% TS as a frosh, 58% TS in his third season.
i could go on, but the point has been made. these are just dudes i though just off the top of my head and just from the last 3 or 4 drafts. if i did actual research, no doubt there are plenty more.