DeGale was victorious in the first round
Olympic champion James DeGale floored Jindrich Kubin to secure a first-round win over the Czech in his second professional bout in Belfast on Friday.
DeGale had won his professional debut in February on points but was widely criticised for the style of his win.
But the middleweight was quickly on the offensive this time, landing a huge left before delivering a series of rights, with the third poleaxing Kubin.
World amateur champion Frankie Gavin stopped Frenchman Mourad Frarema.
DeGale, 23, had begun his professional career with victory over Georgia's Vepkhia Tchilaia at Birmingham's National Indoor Arena but failed to impress many spectators, some of whom booed him at the end.
And the Londoner was given a frosty reception in Belfast when he was booed into the ring.
But DeGale gave the perfect response to his critics with a relentlessly aggressive performance against the Czech, who was boxing outside eastern Europe for the first time.
"The performance was fantastic," DeGale said.
"I put my punches together, the geezer had five wins and no losses, and while I'm not saying he was fantastic he was 5-0 with three knockouts and I went in there and did the business.
"I'm a bit shocked with my own performance really. I knew I could do it. I've gone from my first fight - which when I watch it I cringe - to this.
"It's always been there - I do it in the gym, in training - but it's about transferring the gym work into the ring and I'm doing it now.
"I'm not being big-headed or boasting but I can do what I want - I can box and I can fight."
Gavin had a tougher fight than DeGale, but the Birmingham boxer still managed to secure a third-round stoppage against Frarema.
The Frenchman caught Gavin twice early in the third, but the world amateur champion then produced a flurry of punches, forcing referee Mark Green to step in.
DeGale's fellow Beijing Olympian Billy Joe Saunders also made it two wins from two with victory over Ronny Gabel, making light work of his German opponent with a second successive two-round victory.
Earlier, Chorley welterweight Michael Jennings returned to the ring after his unsuccessful world title shot in February with a fourth-round victory over unbeaten local man Willie Thompson.