By Åsgardian standards (the city they lived in), they were complete small-fry. Buuut their activities there were also very much on the uprise, so the government branded them a potential terrorist threat. They were eventually hunted down, cornered, and they... well, long and complicated story short, they fell off a cliff. Frey (the little fox dude) lost his left hand, and Garm was knocked unconscious and sent down a river. Frey was captured by the Åsgardian army, whipped into shape (literally) and eventually proved himself to be a very dangerous soldier - working for the government he had vehemently opposed since he was young. He now enjoys all the benefits of that, although every fiber of his body wants to get back at Garm for the loss of his hand and the whole 'getting bailed on' thing (again, long story).

Garm was found along the river shore by Fenris, and together they would form the 'Eat the Sun' Syndicate, that exists as a parallell society to Åsgard. They're not fond of the government, but they do coexist with them... somewhat. Garm keeps beating himself up about what happened between him and Frey, but despite everything he has managed to move on - largely due to how he had no guilt in what happened.

It's complicated, but TL;DR - no, they are not very dangerous... unless provoked, which I guess is true for all of us. c':
If anything, Frey's the dangerous one - but only to Garm, really.