Shane Long triggered a ‘dive’ storm then scored as he returned to haunt Albion on a day of controversy at the KC Stadium.
The Ireland international, who was sold by the Baggies in January, won Hull a penalty just after the half-hour when he appeared to throw himself down in the box after no contact from defender Craig Dawson.
Liam Rosenior headed Hull ahead from the rebound after Ben Foster had saved the spot-kick from Nikica Jelavic, then Long rubbed salt into Albion’s wounds six minutes later by making it 2-0.
The striker netted from close-range after poor Baggies defending and then refused to celebrate his goal.
But he had already damaged his reputation with travelling Albion fans, who booed him throughout, and with supporters on social media who accused him of diving.
Albion’s day got worse when their already-depleted squad suffered two more injuries in the second half.
Albion made a bright start and in the opening moments they went close through Stephane Sessegnon, who bent a 25-yard shot just past the angle of post and bar.
The hosts applied some pressure, first when Ben Foster punched clear a dangerous Tom Huddlestone corner and then when Youssouf Mulumbu made a crucial block in the penalty area to keep out a goalbound shot from Albion old-boy Curtis Davies.
Davies was called upon at the other end to make a timely tackle on Victor Anichebe in the Hull box after some neat Albion play.
And goalkeeper Allan McGregor then made a smart save to keep out a long-range Graham Dorrans effort after another clever Baggies move.
But the game turned just after the half-hour when Long went down under pressure from Dawson.
The striker appeared to fall after tripping over his own feet and, while he did not appeal for a penalty, Foy awarded a spot-kick to the fury of the Baggies.
Foster made a fine save from Nikica Jelavic’s penalty but Rosenior converted the rebound with a diving header.
Foster excelled himself again when he flew instinctively to tip a long-range drive from Huddlestone over the bar.
But he could do nothing seven minutes from half-time to prevent Long netting a second.
The striker pounced from close range after a Jelavic cross dropped kindly in the six-yard box thanks to some dismal Baggies defending.
The resentment continued to simmer with Baggies fans booing Long and the striker almost coming to blows with former team-mate Youssouf Mulumbu moments later after an off-the-ball clash.
Hull had a chance early in the second half when Sone Aluku’s cross found Jelavic at the near post but his effort flew into the side-netting.
And Long almost added insult to injury with a fantastic 30-yard effort that beat Foster and rattled the woodwork.
Albion’s best second half chance fell to Victor Anichebe, whose far-post header from a Dorrans corner was saved by McGregor.
But despite the Baggies pressing hard, they rarely threatened McGregor’s goal and Mel’s injury worries deepened as both Gareth McAuley and Anichebe pulled up in the closing stages with what looked like muscle problems.