Well that depends, and in this case we cometo the point were the big differences between goblins arise. Warhammer gobbos are essentially the same as the Goblin Slayer ones, minus the rape and with higher IQ, or well, at least enough to fight in proper formations and have siege weapons.Assuming Goblin Slayer got Isekai'd into Warhammer (Fantasy obviously because 40k is broken, plus gretchins are irrelevant), then he'd quickly have to deal with this boost in intelligence and be forced to up his game. Sadly, I don't see him being able to continue his dyas of soloing goblin hideouts, and even small adventuring parties woudl have a hard time.Initially, he'd probably ally with the locals to repel the greenskins whenever possible, ideally with goblin-only tribes but going throught orcs if necessary. He'd likely join some group of foresters to actively hunt them rather than staying defensive, all the while learning new tactics, including the joys of gunpowder and the unreliability of magic in the setting.Eventually, his extremism and obsession with goblins would put him at odds with the humans, as they usually have bigger things to worry about like beastmen, so he'd eventually fall in with the only crowd just as if not more autistic about killing gobbos: the dwarfs.By the endgame, I could see Goblin Slayer joining Belegar in the Goblin front for the retaking of Karak 8 Peaks, going against Skarsnik.