The 24-year-old Togolese forward, who scored 15 goals in 29 regular-season appearances for Cincinnati, delivered the decider in the first game of the "Hell is Real" Ohio rivals playoff matchup.
Cincinnati, the second seed, took a 1-0 lead in their best-of-three first round series, which continues on Sunday in Columbus.
The series winner will meet either Lionel Messi's Inter Miami or Nashville in the Eastern Conference semi-finals.
The night's only other match saw Minnesota win a penalty kick shootout 3-2 over visiting Seattle after a goal-less draw to grab the lead in their Western Conference series.
Minnesota goalkeeper Dayne St. Clair stopped Seattle's Alex Roldan in the second round of kicks and when Cristian Roldan hit the crossbar for the Sounders, they were on the brink of defeat.
Julian Gressel hit the post for Minnesota but when Seattle's Danny Leyva then hit the left post, United had the hard-won triumph.
The winner faces either top seed San Diego or Portland in the West semi-finals.