Why did Marlo kill the girl?
Keeping this in consideration, who was the girl Marlo killed?
Partlow drove by the car and shot and wounded Avon and killed another Barksdale soldier. Marlo and Partlow later tracked Devonne to her home and Marlo murdered her personally as she was leaving one night. The violence continued to escalate and Marlo's lieutenant LaTroy was killed.
Thereof, why did Marlo kill Joe?
He was getting the dope right off the boat from the Greeks and with all the west side real estate Marlo had Prop Joe knew he could sell him multiple kilos every resupply. Prop Joe also needed muscle to help run the NY dealers out of the east side. Marlo had Chris and Snoop who killed at least 5 of them.
In another nod to the real man, the series featured a cop named Oscar Requer in its final season. Timmirror Stanfield (inspiration for Marlo Stanfield): Marlo Stanfield is a cold-hearted killer and businessman.