Reverse Collapse: Code Name Bakery - Chapter 3-6 Oleg Boss

Playthrough of the Oleg fight in Chapter 3-6.
First thing to know for this boss is that you need to drop him to 4.8k HP, not 3k HP. You should also avoid using normal attacks on him unless absolutely necessary - use items and skills instead.
1. Jefuty's Collapse Bombardment skill can wipe out a sizable chunk of his health. You should invest in that skill.
2. If you need someone to use normal attacks, use Jevon. His shield can protect him from a good number of Oleg counterattacks.
3. Use your flashbangs. This will make Oleg's escort easy pickings. Flashbangs can't stun Oleg, but they do debuff him substantially.
4. Send Atena to the far-away collectible and purple items. By doing this, it will be safe for Jefuty to die to Oleg a few times.
5. Medium and standard turrets, RC bombs, and rocket launchers are particularly effective against Oleg and his (stunned) escort.