Is it possible to use Berserk against charging Lost Souls without taking damage?
I was wondering if perfect timing would allow you to punch Lost Souls just when their charge reached you, without taking damage.
Yes. Berserk isn't even necessary, as lost souls have a 100% pain chance. Any hit will stop their attack, even if it doesn't kill them.
Source: I tried it myself and it worked.
This isn't a satisfying answer on its own, so I'll try to throw in some numbers to show why it works. I can't guarantee this analysis is correct, but the outcome is. I'm assuming collision boxes don't matter and that the fist's hurtbox extends outward from the edge of the player's collision box, not from the center.
https://doomwiki.org/wiki/Lost_soul have a movement speed of 20 units per tick during their charge. A https://doomwiki.org/wiki/Tic is 1/35th of a second. The https://doomwiki.org/wiki/Fist has an attack range of 32 units.
The fist has a longer range than the lost soul moves in a single tick, therefore there is a 1-2 tick timeframe, or 28-57ms, for the attack to connect while the lost soul is in range but has not yet collided with the player. Presumably moving backwards would extend this timeframe.
The https://doomwiki.org/wiki/Chainsaw can also be used; it has a slightly longer range (33 instead of 32) and deals damage every 4 ticks. This would suggest that the chainsaw will stop roughly half of incoming lost soul attacks. If running backwards does work as I think, this would make the chainsaw work every time, as the https://doomwiki.org/wiki/Player has a running movement speed of 16.67, meaning a charging lost soul is in range of the chainsaw for 8 full ticks.