Chris Eubank Jr dropped Liam Williams four times but had to settle for a points victory over his rival.
The two middleweights finally touched gloves in Cardiff following two postponements of their grudge fight.
And Eubank Jr raced out of the blocks, dropping Williams three times in the first four rounds.
The Welshman battled back but a fourth knockdown in the 11th round ended any hopes he had of a stunning comeback.
All three judges gave Eubank Jr the nod by scores of 116-109, 116-108 and 117-109.
"I'm happy with the performance, I wanted to teach this man a lesson, he'd said some menacing things to me leading up to this fight and I wanted to punish him," said the winner.
"I thought about it, I didn't even want to knock him out in the first round, I wanted to punish him, I wanted to get people like that out of boxing. You saw it, head locks, head butts, I took it like a man and punished him like I said I would do."
Williams had established his jab and taken the centre of the ring in the opening round but was caught by a jab which dumped him on the canvas.
The home favourite recovered to beat the count but looked shaky until the bell.
And he was dropped again with a minute of the second session remaining as he struggled to deal with Eubank's speed.
Williams was more controlled in the third round as Eubank hit his rival after the bell which prompted a furious reaction from referee Mark Lyson.
But another jab sent Williams to the deck again in the fourth round as the Welshman unravelled under the bright lights.
Willams composed himself in the fifth and sixth rounds but Eubank Jr was confident enough to showboat to the crowd in response to his opponent's attacks.
The Welshman began to work his way back into the fight and had clawed back some of his huge deficit by the end of the eighth session.
Eubank Jr has lost his swagger as the fight entered the final three rounds with Williams continuing to land the more eye-catching shots.
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But any hopes Williams had of a stunning comeback were extinguished in the penultimate round when he was dropped for a fourth time - although replays showed Williams had stumbled.
Willams attempted to finish strongly but his fate had already been sealed as the judges handed in their cards.
On the undercard, Chris Jenkins outpointed former super-lightweight world champion Julius Indongo over eight rounds, much to the delight of the home crowd.
Olympian Caroline Dubois made a winning start to her professional career as she followed in the footsteps of heavyweight brother Daniel.
The 21-year-old won each of the six rounds against Vaida Masiokatie with the promise of much more to come.
And multiple-world champion Claressa Shields kept her side of her deal with Savannah Marshall ahead of their prospective super-fight later this year.
Marshall must beat Femke Hermans next month in a defence of her world title after Shields dominated Ema Kozin over 10 rounds to retain her three middleweight belts.
