that chaingrab should be all the evidence you need.While I never considered anyone in particular "OP", I have heard the most from friends that Meta Knight and Ice Climbers are OP. Meta Knight I can understand, because some of his sword moves are insane, not to mention an incredibly powerful B-up where you can just fly back on the stage. Ice Climbers I never really could understand aside from that chain grab, and I was never particularly good with them, either.
That chaingrab alone gives them the ability to 0-death any character in the game.
it doesn't really matter if you aren't that good with em/can't do the 0-death with em yourself. Its still there, and its still single-handedly makes them insanely good.