Giant predators and how to defend yourself against them

I've been reading a lot of stories regarding felarya, and somethings been bothering me. In one of the stories it has a bunch of video game characters that get suddenly warped into felarya, and somehow Masterchief, who is in the story, gets eaten by a dridder and blows open the dridder using a plasma grenade. But aren't giant predators in general resistant to explosives in their stomach? I mean, look at Crisis, who was able to resist a frag grenade exploding in her stomach. But this dridder exploded rather violently........

Which brings me to this point........what REALLY is powerful enough to hurt a giant predator? I read felarya express and somehow the captain french guy has a plasma pistol capable of seriously hurting a giant predator, so why won't a grenade do anything? Lists would be helpful.

You should read this thread

First, Crisis is noted as having an exceptionally tough stomach.

Second, Halo firepowers. We're speaking a universe where you can create something like a 30m diameter glassed crater with standard covenant artillery. Game mechanics are quite different from novel (in which case MC does much better, as this was a guy who outside Power Armor was kicking people in builkier suits several meters through the air. In his early teens).

(Locking since we already have a thread for this)