Dundee United made Kilmarnock pay for Liam Kelly's red card with a second-half demolition of Kenny Shiels' team.
Kelly was sent off for a foul on Gary Mackay-Steven 10 minutes into the second half and striker Jon Daly rattled home the resulting penalty.
Paul Dixon hammered a long-range strike through Cammy Bell's arms, then John Rankin hit a shot into the top corner.
And Scott Robertson rounded off a smart one-two for the Terrors' fourth for their biggest home win of the season.
The win for Peter Houston's side lifts them above Kilmarnock and into the top half of the table.
The result was harsh on Bell, who made several excellent saves in the match, including two from Rankin and a block from a Johnny Russell effort.
Daly passed up a glorious chance after five minutes after good work by Sean Dillon and Russell, knocking the ball over the bar from four yards, and he blazed over again on the stroke of half time when a pass to Russell may have produced a goal.
Russell continued to be the heart of every United attack and he should have done better when he met Dixon's cross at the front post after 30 minutes.
The home side almost took the lead in controversial fashion when Rankin's free-kick, which was intended to be sportingly returned to Bell, looped just over the bar with the goalkeeper out of position.
The first half ended goalless as United were unable to convert their superior possession into goals.
In the first minute of the second period, Daly laid the ball off to Rankin and his left-foot crack at goal was tipped over by the Killie keeper.
And soon after that, Bell kept the scoresheet blank when he saved from Scott Robertson and then from Russell who had controlled a cross by Willo Flood and evaded centre-half Michael Nelson.
The match turned on Kelly's sending off, as he made contact with Mackay-Steven as he waited on a header landing.
Daly made no mistake from 12 yards, hammering the ball into the corner of the net, and giving Bell no chance, though he guessed the right way.
United's second was a howitzer from Dixon, who later hit the post with a shot.
Bell prevented United's third when he turned a trademark Rankin 30-yard squiggler round the post.
The visiting keeper punched Flood's corner clear but only as far as Rankin, who took one touch to control the ball before arrowing a shot into the top corner of the Killie net with 20 minutes to go.
At the other end, Nelson failed to trouble Dusan Pernis with a close-range header as the visitors tested the United keeper for the first time in the match.
But United were soon attacking once more and when Robertson worked a one-two with Stuart Armstrong he found himself with only Bell to beat, which he did with aplomb in the 84th minute.
Dundee United manager Peter Houston: "It's good to take all three points and put in a good performance too.
"After Saturday's poor performance on the ball, I thought the lads were excellent tonight.
"We scored some cracking goals, we asked the guys to shoot and try to be less intricate and going on the second-half display we didn't have to ask twice.
"I am really pleased for John Rankin. It would have been a disappointment having been let go by Hibernian, but he has responded with a number of excellent performances - it wouldn't be a surprise to see him receive a number of the supporters awards at the end of the season."
Kilmarnock manager Kenny Shiels: "It was a poor performance. There were contributing factors but they were the better team.
"I was disappointed in Craig tonight, I thought he was off the pace, as we were. He struggled to keep up with play and handed out cards like confetti.
"That isn't why we were beaten, though, we were beaten because the best team on the night won the game.
"We are going to try and correct our frailties after tonight and the referee maybe needs to look at his performance and try to improve too."