Found in stasis-lock on a salvage ship by Sunspot and repaired by the Freedom's medical staff, Avalanche originally intended to return to the Autobots despite a bad case of amnesia. But when he found his old teammates only to learn it was their betrayal that had nearly killed him, he realized that his idealized view of the Autobots didn't quite match reality. Sobered by this revelation, he decided to stick with LONAC.
Avalanche is a laid-back, easygoing 'bot. He doesn't shy away from battle, but is happier relaxing and just hanging out with friends. And now, away from the Autobots, he's found it much more satisfying to fight for his friends than for vague ideals anyway.
As his memory slowly returns he has found himself having to deal with all the pains of his war-torn life all over again, and more often than not he's sought to deal with this through frequent visits to the Freedom's Neutral Ground bar. While his memories have reminded him of his resolve to fight the Decepticons, they have also served to remind him of the losses brought on by constant warfare. As a result he's become deeply conflicted between his ingrained role as a soldier and his desire to keep his new friends from suffering the fate of his lost Autobot friends. Fortunately for the other bar patrons he's a jovial drunk.
In vehicle mode Avalanche's heavily-treaded tires give him traction on almost any surface. His relative size gives him an advantage over comparable foes in close combat. Most of his Autobot combat training has remained intact despite his memory loss, making him a skilled fighter. The only weapons left with him when he was found were his shoulder-mounted canister missle racks, but he can also use a variety of hand weapons based on what's available.
Avalanche is relatively bulky, and this places serious limitations on his agility and speed in both modes. Despite his traction abilities he doesn't have the ground clearance of more dedicated all-terrain vehicles.