Eight-man Hearts fell apart as they were over-run in a miserable second half at Tannadice.
The Edinburgh side lost all sense of discipline as three players were sent packing and it could have been more.
It smacked of a club in complete turmoil with no-one apparently able to demonstrate any form of leadership.
Inevitably, they were unable to hold back a resurgent United and the final scoreline, which included a hat-trick from captain Barry Robson, did not flatter the Terrors in any way.
The match ended in total contrast from the initial subdued atmosphere as the fans came to terms with the loss of former Motherwell captain Phil O'Donnell.
After 23 minutes of little quality, United were gifted the lead courtesy of an error from Robby Neilson.
As the Tangerines switched the ball around the edge of the box, the defender hooked it high back to his keeper, giving Steve Banks little option but to clear with his hands.
From the resulting free-kick four yards out, Lee Wilkie touched the ball to Robson, who thumped it high into the net.
But Hearts came back with a fighting spirit and it was no surprise they equalised in the 37th minute through Christophe Berra.
A Michael Stewart corner was touched on by Calum Elliot and, with the Tangerine defence sleeping, the captain flew in to stab home from eight yards.
The second period opened with United in ascendancy, but it was a moment of madness from Marius Zaliukas which brought controversy and changed the game.
The defender took a swipe at Wilkie and was rightly red-carded, but with the ball apparently out of play the referee consulted his assistant and awarded United a penalty which Robson duly converted.
It was game over in the 84th minute when Noel Hunt headed in Robson's curling free-kick.
Stewart had been duly cautioned for flattening Robson and he was fortunate not to walk for his reaction, but his team-mate, Lee Wallace, was sent to the dressing room in the 86th minute for a last-man tackle on Robson, who again stood up and hammered home the penalty.
Red mist had spread across all the Hearts players and it was no surprise that on the stroke of full-time Stewart became involved in an altercation with the assistant referee and some of his own supporters and was sent for an early bath to conclude a miserable afternoon for the Edinburgh side.