So as far as I recall, Loki did "lose it", but not quite in the way you're thinking.
You see, what kicked off Ragnarok was Loki tricking the blind god Hod into slaying Baldr, the god of light, and then he's implied to have stopped Baldr from being returned from Hel by refusing to weep for him in disguise. The gods then avenged Baldr by chaining up Loki.
When Ragnarok comes, Loki is unbound to fight with the giants and he fights Heimdall, both dying mutually.
What's interesting is that a lot of people I've seen online seem to feel Loki was OOC in doing this, as before he was more of a trickster or prankster.
It's not clear why he went so far. Maybe it was out of jealousy because Baldr was beloved, maybe it was to bring Ragnarok about.
For my part, despite his name, I think Loki in OP is more likely to wield Surtur's power. It fits with his rage and destructiveness, it fits Surtur being the fire giant and it's a fruit that could easily be mistaken for a Sun God's.
And Surtur IS a berserker - he's responsible for burning down everything at Ragnarok after all. That might suit your taste.