OS SRMs(iOS if available), as many small racks as possible, loaded with Infernoes. Jump 4-6 hexes right in front of it, entice it to fire off all those guns at dicey to-hit rolls, then bathe the beast in napalm. (Multiple small racks because your own numbers will also suck, so you want quantity of dice to compensate)
If you lose initiative next turn, back up enough to try and taunt it into chasing after you and shooting, don't let him think he's got a chance to pull back and cool down. If you win, jump behind him, fire the lasers aimed high (the Atlas won't have crap for a TMM due to the heat), and then kick him in the back of the knee to try for a knockdown. If any lasers score a head hit, immediately start positioning yourself for a DFA, that's one of the only ways barring TACs to quickly kill an Atlas.