UK light heavyweight Buatsi secured a victory yet unimpressive start to life under fresh promotional backing with a unanimous decision over Zach Parker in Manchester.
The Olympic medal winner's activity level likely gained him a judges' verdict in a competitive ten-round contest at the boxing arena.
But the challenger landed significant shots, connecting with powerful clean blows in a match where the styles failed to mesh, with constant grabbing disrupting the fight.
Two judges scored it 96-94 for to Buatsi, with the third a 95-95.
"It wasn't my best display but what defines champions? They succeed," the victor stated in the arena as he was met by boos from the audience.
The British fighter got back to winning after his initial pro loss - an epic battle with Callum Smith in February - to secure a twentieth professional win.
Some ringside observers believed Parker, 31, merited the win but the British boxer endured the second setback of his 28-match career.
Buatsi Earns Triumph in Slow Affair
The fighter's advancement has slowed in recent years through contract problems and considerable time of lack of fights.
Previously predicted as the future of British boxing, he now finds himself trying to achieve expectations - perhaps in what seems like a last chance - under recent support.
He started carefully, with both competitors ready to be aggressive in a tentative opening few rounds.
The challenger, whose single earlier setback came at super middleweight against John Ryder in 2022 after damaging his hand in the contest, was participating in his second bout at light-heavyweight.
By the middle rounds, the underdog had kept it close, creating difficulties for Buatsi, who utilized a tight guard to narrowly win the cleaner stanzas.
The crowd's patience decreased because of constant clinching, with the challenger falling to the floor multiple occasions during grappling.
The underdog finished the stronger, but multiple periods were difficult to score. Nevertheless, previous titleholder Carl Frampton - providing analysis for Dazn - had it significantly in favor for the challenger, giving Buatsi just only one stanza.
The victor progresses, but with the caliber of hard hitter Benavidez, and Russian champion Bivol leading the category, the road to world glory - on this evidence - still seems difficult.
Ricky Hatton Homage Inspires Manchester Derby Contest
In the secondary fight, Arthur overcame Bradley Rea by close verdict in a outstanding local rivalry contest to win the European light-heavyweight title.
The arena became quiet for a deeply poignant memorial before the fight as a bell ceremony sounded in memory of local hero Hatton, who succumbed aged 46 in recently.
It was the premier televised boxing event in the urban center since Hatton's death. As the final chime ended, the silence transitioned to a shout of "there's just one Hatton".
The action during the bout reflected the sentiment. The eventual winner was knocked down by a powerful punch flush on the jaw in the second round, rising shakily to his position on the eight count.
But the traditional red shorts of Arthur soon advanced again. From the other corner, the opponent - in competitive blue - was injured quickly, significant bruising appearing under his eye as the pair landed powerful shots.
The challenger, 27, connected with strong blows but the champion, thirty-four, matched the intensity with effective uppercuts as the intensity seldom decreased over the full distance.
Arthur barely secured the result with judges scorecards of even score, close margin and wider gap, but the two athletes were determined and full of heart, exactly what their inspiration the legend embodied.
