Easter Egg: The LOST Wheel
Immediately after upgrading the TMD to its final level (where it does not use TMD Energy for all attacks), break the vent behind the upgrade machine. The crawlspace leads to this easter egg and some game related items.
Ending 1: After disarming Demitov, turn around and use the TMD on the portal. Neutralize past Renko (headshot) for this ending.
Ending 2: After disarming Demitov, turn and neutralize Barisov for this ending.
Ending 3: After disarming Demitov, neutralize both targets for this ending.