Act II - Nightfall / DARK LABYRINTH ("Go through the ruined house") - I showed my method in the video.
This is the perfect time to collect "Kill 3 enemies at once 10 different times".
After kicking through the door, we go further to the right where several enemies run out,
then throw a grenade (so that it bounces off the wall and lands close to our opponents
instead of flying somewhere far away), and even if we die or if we survive then commit suicide
(going back to the moment before the door), these grenade kills are not lost.
This is counted so after respawning we can continue in the same way until we get achievement.
Unfortunately, there is no pop-up window with recorded achievement
(as you know, recorded clips from games on Xbox One as opposed to backwards compatible with Xbox 360
they don't rip achievement pop-up notifications into the video, even if we're recording
through e.g. twitch).