K-9000 is a robot dog Amigo from the paid Blood Dragon Bundle, a nod to the Robo-Dogs of Far Cry 3: Blood Dragon. If you own the bundle he joins your roster without a mission.
Buy the Blood Dragon Bundle and K-9000 appears in the Amigo menu. There is no Yaran Story for him.
His resistance to fire and poison means you can send him into flamers and gas without losing him. That suits fights against Flamers and poison-armed squads.
Alfredo Máximo
Alfredo Máximo, called The Bouncer, is a La Moral soldier with a smooth tongue who ends up as one of your Los Bandidos operatives. He is one of the leaders you can send on Bandido Operations.
Image: UbisoftBoomer
Boomer is the dog from Far Cry 5, back in Far Cry 6 as a stealth Amigo that Dani calls Boom-Boom. He tags enemies around you and pulls loot off bodies, which makes him the best pick for scouting a base before you go in.
Champagne
Champagne is a white cougar Amigo that only comes with the paid Vice Pack. If you own the pack, she joins the Amigo roster without any mission to unlock her.
Image: UbisoftChicharrón
Chicharrón is a punk rooster Amigo raised for cockfights who would much rather peck FND soldiers. You earn him in El Este by helping with his grudges against the regime.