CCTV footage shows Ramani Sanderson lunging at Shane Mayer with a sword outside Gabba's Bar in Darlaston on the night of July 24, 2019.
Sanderson, 20, was convicted of Shane's murder on Wednesday by jurors following a trial at Birmingham Crown Court.
Fellow defendants Joseph Till, 21, and Kamron Reid, 20, were found not guilty of murder but convicted of manslaughter. Lewis Green, 21, was cleared of murder and walked free from court.
Sanderson, of Walsham Road, near Peckham, London; Reid, of Herberts Park Road, Bloxwich and Till, of Summer Street, Willenhall will be sentenced at a later date.
Detective Sergeant Andy McDonald, from West Midlands Police's homicide unit, led the investigation and welcomed the guilty verdicts.
He said: "This is yet another example of the devastation caused by knife crime. A stray glance and words exchanged between strangers has escalated to murder in the space of just 15 minutes.
"A young man’s life has been ended in tragic circumstances and the lives of those responsible for his death are now ruined.
"Sanderson stabbed Shane but we firmly believe the others were armed.
"I know this awful crime has had a devastating impact on the Shane’s family and that they are still struggling to come to terms with his death.
"I hope the fact his killers will now face many years behind bars offers some comfort."