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

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

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

step 3:after the cut scene tu will fight the pain.
when he is wraped with bee's through a
grenade at him o 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 & tu shuld kill him
in a few minutes.