Jello is the low man on the totem pole. This much we know from the fact that he's basically a babysitter for the pups, while the other adult wolves go out on the hunt.
Even though it clearly tires him out, he's forced to roughhouse with the pups to keep them busy,
A tense relationship develops between Jello and Miyax. She tells him (in wolf language) that she's the boss, but they compete for food. The two have a dispute over the caribou the other wolves have killed, and at the end of Part 2, Jello steals all her food. Not cool, Jello!
He leaves with the pack to start their nomadic winter life, but it's clear he's barely a member of the group anymore.
Early on in their winter travels, Jello steals Miyax's pack, with all her food and supplies in it. He needs food just as much as she does, after all.
This turns out to be a terrible idea. Because he threatened Miyax's safety, Amaroq and the rest of the pack turn on Jello and rip him to shreds, resulting in his death. The message is clear: don't mess with Miyax.