Tier S+: Eye Guy; Wildvine; Lodestar; Arctiguana; Blitzwolfer; Transmutor; Upgrade; Overflow; Soulcatcher; Terrorsaur.
Tier S: Heatblast; Diamondhead; NRG; Shellhead; Ball Weevil; Brainstorm; Ditto; Armodrillo; XLR8; Warp; Gurge; Lurk; Ampfibian; Ghostfreak; Snakepit
Tier A: Water Hazard; Pesky Dust; Gravattack; Bloxx; Crashhopper; Gray Matter; Skidmarx; Crabtastic; Bashmouth; Gutrot; Gax; Braindrain; Skele-TON; Cannonbolt; L'Goon; Astrodactyl
Tier B: Kringl the Summoner; Mole-Stache; Stinkfly; Ripjaws; Shock Rock; Murk Upchuck; Mealymouth
Tier C: Shocksquatch; Big Chill; Perk Upchuck; Funguy; Clockwork; Wildmutt; Snark Tangue; Somnambulizard; Hippopotamass; Sandbox
Tier D: The Worst; Swampfire; Chromastone; Echo Echo; Jetray; Feedback; Whampire; Squirtapiller; Nanomech; Buzzshock
Tier E: Rath; Kickin Hawk; Atomix; Bullfrag; Slapback; Alien Z; Goop; Decagon Vreedle; Spidermonkey; Snare-oh; Spitter; Jak the Freeze; Toepick; Way Big; Terraspin; Ventrilosquid; Four Arms; Humungousaur; Frankenstrike; Moyo
Tier F: Alien X; Fasttrack; Eatle; Chamalien; Walkatrout; Surge; Antigravitesla; Invincible; Decimus Prime; Portalier; Juryrigg; Shadowman; Squidstrictor; Plantapocalypse; Bungee Sponge; Rocks; Bob the Blob; Stretcheleo; two last losers whose names I couldn't find
Link to original template:
I can't believe how long and hard it was to find all these names for non-canon aliens.