Sade Samanter, 21, was convicted of murdering Abdullahi Osman in Ealing on 11 August last year by a jury at the Old Bailey earlier.
Ibrahim Dualeh, 34, admitted murdering Mr Osman, at a hearing on 2 October.
Samanter, of Southall, Middlesex; and Dualeh, of no fixed address; will be sentenced at a later date.
Officers discovered Mr Osman, from Uxbridge, collapsed in Dean Gardens, The Broadway, West Ealing.
The 31-year-old Somali national was taken to St Mary's Hospital in Paddington where he died two days later.
Det Insp Simon Ashwin, of the Metropolitan Police, said Mr Osman had been assaulted during an unprovoked, drink-induced attack.
He said a third man, Mohamed Jeylani, 24, was charged with grievous bodily harm but the case was discontinued.
Mr Jeylani was released with no further action.
The Victim:
The Murderers, Sade Samatar on the left and Ibrahim Dualeh on the right.
