Community's non-official tier list. Day 20: Ditto

Am I the only one who thinks about the alien before the pokemon when hearing the word "Ditto"?

Most upvoted comment decides his spot on the list.

I'm not going to include ultimates, fusions or aliens outside the main series, just the 67 aliens that appeared and were used by Ben on-screen. Ken's Sandbox, Shellhead and Snakepit aren't included

Reboot aliens Overflow, Gax, Shock Rock, Slapback and Surge are going to be included at the end

I didn't find anyone doing this before, so I'm attempting to do this now. If someone already beated me to it, please let me know. I'll just delete this tier list.