Pontiff Sulyvahn (Defeat Pontiff Sulyvahn) and Aldrich, Devourer of Gods (Defeat Aldrich, Devourer of Gods) in Dark Souls 3. Probably the hardest fights I've had on my playthrough thus far so I'm more than pleased with myself.
"Champion Gundyr" for defeating Champion Gundyr, "Archdragon Peak" for reaching Archdragon Peak, "Supreme Weapon Reinforcement" for reinforcing a weapon to the highest possible level, and "Lord of Cinder: Lothric, Younger Prince" for defeating Princes Lothric and Lorian. All in Dark Souls 3 of course.
I had a pretty good night last night to say the least.