Lost souls are more of a nuisance than a threat, honestly, since they tend to just end up crashing into eachother and then getting into a massive infight-fest until there's only one or two left. EXE had a hard limit of 20 lost souls at a time If there were 20 or more of them at a time, PEs couldn't spawn any until their numbers dropped, so it's hard to actually get a huge swarm unless you're using a source port that allows you to disable that limit. Annoying if they're on the other side of a huge open area, though, since then they can just keep spamming at you and you don't notice until you're knee-deep in the dead-er, in lost souls. Or you could just hit them with rapid fire since they go into pain 50% of the time. You can literally just stand there and punch them to death and there's nothing they can do to stop you. They're incapable of doing anything if you're right up in their face. I haven't actually played Doom 64 so I can't really comment on those ones (other than OH GOD WHY DO THEY SHOOT TWO AT ONCE WHOSE IDEA WAS THIS), but Pain Elementals in Doom 2 are not a big deal at all.