Like Susan, his last appearance happens during the alternate-universe episode.
NBC
Last appearance: Season six, “The One That Could Have Been, Part 1”
As the main friends imagine what their lives would’ve been like if some things had gone differently, Rachel thinks of an alternate universe where she married Barry.
She also meets Joey, who’s a successful soap-opera star, and considers cheating on Barry with him. She can’t bring herself to cheat on her husband, but when she gets home, she finds Barry in bed with another woman.
Barry’s last line is, “You said you were gonna be away all weekend!”