The worst call to take place in a Seahawks game was the play Bowman got injured on in the NFCCG. The worst part was that SF couldn't even challenge because of some quirk in the NFL rulebook. At the time of course, I was elated to catch this break, but man, it was so shitty. I'm glad that justice as served on the next play, and that we still won in awesome fashion. Had to feel sorry for Bowman though, horrific injury, gets screwed out of a critical turnover in the 4th quarter, and then has popcorn poured on him as he rides off the field on a cart.
The worst call against Seattle would be one of many from the Indy game. There was a phantom PI on Browner where he did not even touch the guy or the ball was overthrown by 15 yards or both, I just remember it being a are you effing kidding me kind of call. That call that wiped out a punt, and the Colts would later score a TD on the same drive, IIIRC. That call was probably the difference in the game. There was also a really awful OPI call on Tate in that game.
I wouldn't consider it a terrible call, but I thought the refs got it wrong when they didn't overturn the interception at the end of the Arizona game. I thought I saw a few specs of turf kick up, plus physics demand that a ball would never bounce at that angle without touching the ground.