During the entirety of the Omega DLC, you’ll be able to influence Aria’s behavior, which will ultimately decide Oleg’s fate.

Choice: Spare or Choke Oleg¶

Throughout the DLC you’ll have various options to persuade Aria to think of the civilians who live on her station, or you can push her to be more vengeful, if you’ve been using a mixture of these choices, Aria will bring this up, giving you a chance to still affect the outcome.

Choice: Spare Oleg (Paragon)¶

By repeatedly telling Aria to think about the civilians living on her station, she’ll spare Oleg, and let him live, resulting in her ending speech comforting the civilians, and her promising to protect them.

Choice: Choke Oleg (Renegade)¶

By repeatedly telling Aria to seek out vengeance, then at the end, she’ll choke out Oleg, leaving him dead, resulting in her ending speech encouraging the civilians to do as she’s done, and enact revenge on Cerberus.