Greenwood, the former Manchester United forward who made a controversial move to Marseille this summer, had a hand in all five goals on Saturday as he also provided two assists and won a penalty that Elye Wahi converted.
Greenwood's first Ligue 1 appearance was greeted with boos that echoed throughout the Francis-Le Blé stadium every time he touched the ball. The 22-year-old forward was arrested in 2022 and later charged with attempted rape, controlling and coercive behaviour and assault. The case was dropped last year.
Brest, who finished third last season and are set to compete in the Champions League, struggled throughout the match. A missed penalty by Romain Del Castillo in the first half highlighted their lack of precision.
"This was not our level," Brest head coach Eric Roy said. "We gave them way too much space on the defensive end."
After PSG's 4-1 win over Le Havre in the season opener on Friday, Marseille lead the standings on goal difference after coach Roberto de Zerbi 's first game in charge.
Lille's 2-0 victory over Reims was overshadowed by the head injury sustained by Gomes, an English attacking midfielder, after a collision with Reims' Amadou Koné in the 11th minute.
Gomes received medical attention for more than 20 minutes before being carried off on a stretcher. The 19-year-old Koné was shown a red card.
Lille later said on social media that Gomes had regained consciousness and was taken to a hospital for further evaluation.
"Angel is doing pretty well," Lille's club president Olivier Létang said. "But we'll wait to find out how he spends the night, with his additional tests, before saying that we have a clear happy ending."
When the match resumed after a 35-minute break, Lille quickly took control. Bafodé Diakité opened the scoring just before halftime, and Canadian striker Jonathan David sealed the victory in stoppage time with a goal assisted by Ethan Mbappé, the younger brother of Real Madrid star Kylian Mbappé, who made his first appearance for Lille.
After the final whistle, both teams posed with a Reims jersey with the words " Take care Angel " written in French.
The final match on Saturday saw Monaco secure a 1-0 win against recently promoted Saint-Etienne after Takumi Minamino scored with a chip over the goalkeeper midway through the first half.
Minamino also appeared to have netted about 10 minutes earlier before it was disallowed following video review.
That was the first of two goals canceled out by VAR, along with a second-half penalty kick that was originally awarded to Monaco.
The other disallowed goal was one that briefly had Saint-Etienne thinking it had leveled the match in the 73rd minute.
