Here's why I don't think Jiggs could ever be called worst in the game:
Once upon a time, probably 2 or 3 months ago, I went into For Glory with Jigglypuff, not too long after picking up the character. Looking for training, I kept going, slowly starting to win more and lose less. Then, I came across a shiek player.
Now, pretty much everyone can agree that shiek is the best character in the game. All of her moves combo flawlessly, she lacks kill moves but has kill setups, an almost completely invincible recovery, etc. etc. now, the person playing this shiek was clearly much better than me. They were consistently beating me in neutral with better spacing and reading, and I was having trouble getting on any % at all. After getting bodied up to my last stock at 100%, I finally managed to score a Bair and kill them somewhere in the range of 120%. With the small momentum from the kill, I managed to get a good string on them and tacked up 40%, before they reset to neutral and hit me up to 142%(the highest I've ever lived to with Jiggs) with needles and other weak moves. I would die to pretty much anything that hit me, right?
Then, he runs in to go for something. I spotdodge his grab and kill him at 40%, give or take.
Despite playing against someone clearly better than me(I switched to Toon Link afterwards and got destroyed) who was using the best character, I was able to make one read and kill my opponent at 40%. I'm pretty sure there's no other character in the game who can do that.