when i fighted the pain it took me an hour too beat him couse i was allmost out of ammo.here is another way too beat the pain more qiuckly.

step 1:when you are in the secend part of the cave
there will be two big hole's take the right
hole head north & there you will find a
shotgun.

step 2:go back (do not go under the the rock couse
it will take you more time)& head to the left
hole & head north.then there will be a cut
scene.

step 3:after the cut scene you will fight the pain.
when he is wraped with bee's through a
grenade at him or the easy way shoot him
with the shotgun.shot him then the bee's
will fly away.keep doing that when he is
wraped up with bee's & you shuld kill him
in a few minutes.