A few that immediately came to mind:
1. Steve Nash after Dallas → Phoenix
2. James Harden after OKC → Houston
3. Jalen Brunson after Dallas → New York
4. Victor Oladipo after OKC → Indiana
5. Jermaine O’Neal after Portland → Indiana
6. Chauncey Billups after bouncing around → Detroit
Shai Gilgeous-Alexander after Shitters -> OKC
Without a single doubt in my mind my answer is Jimmy Butler when he left the Sixers. He was never a scrub or anything but when he got to Miami he took another insane leap.
Dennis Johnson - Seattle and Phoenix 》Boston
Probably Brunson.
Dallas and OKC being on the list multiple times is crazy.
Don't forget SGA after the Clippers or Haliburton after the Kings.
Lowry to the raptors is an underrated one
He was finals mvp in Seattle
He was finals MVP and All-NBA in Seattle
Isiah Thomas to the Celtics. Always respected his game, but fifth in MVP voting averaging 29 ppg? What the actual fuck?
He was finals MVP before Boston
SGA
NAW Timberwolves to the Hawks this past season. Became a 20 points per game scorer.