Probably the Ark or the Earthrise vans. I don't have any interest in the Ark's robot mode, just the ship, and it's severely compromised to accommodate the robot mode. Especially the gaps on the sides for the legs to bend.

The vans were disappointing to me, too. The roofs were poorly done/prone to warping, the van doors were missing, and the arms were way too hollow. Normally hollow spots are well enough out of the way, but the vans had very noticeably hollow forearms. I hope the SS86 van mold is better.

I actually liked Tracks and Arcee. They both looked good. I like Arcee's alt mode better than the T30 mold. Tracks looked good in both modes, he just needed a bit of work to stand up straight. After fixing him up, he's an OK figure.

 

There was only one figure i bought where I was like... Hmmmm i could have skipped this. Double Dealer. For me the legs loose as hell and hated the transformation of said limbs. I'm lucky i got it at half the price it was.

Er/kd/ss Arcee just no big turn off. So mad they rereleased her in kingdom when we could have gotten another beastie.

And ER thrust cause I want him and target said nope scalpers only so im jelly and hate him now, also unfriending him and disliking all his vids.

 

The red partsforming loser.

...Wait a minute, there were three red partsformers.

I mean the red partsformer whose partsforming bit doesn't even look like a shield as advertised (or even any kind of actual accessory) unlike Ironhide and Warpath.

Honestly though, I started skipping most of the WFC line with Earthrise because they seemed either bad or bland to me, so there might be worse figures than Cliffjumper.

 

This will be an unpopular opinion but for me BW Scorponok. The beast more transformation was just underwhelming. Next would be Blackarachnia followed by Waspinator. Also a little underwhelmed with Optimus Primal. I am in no way a G1 only person and enjoyed Beast Wars and really wanted to enjoy these figures but for me they just seemed like Hasbro was intentionally trying to sabotage future figures from Beast Wars with these updates. I would probably feel the same with Rhinox if I didn't skip since I had the Generation mold.

 

Kingdom Ultra Magnus. A €60+ toy and they give you that godawful truck mode?

Honourable mentions:

Ravage. How were they not ashamed to release that? But then, they released Titans Return Ravage before so they're immune to shame.

Cyclonus. Hate that face and I don't like the blocky legs.

Airwave. Ugly head. Should have been a Titan.
Ironworks. See Airwave.

Rattrap. I just hate the character and that ugly face.

Apeface. Peg broke on shield shortly after I bought him. Gorilla head is ugly with that visor and teeth that look like they were drawn by a child.

Airrazor. My favourite Maximal but I bought her twice and her wings are annoyingly easy to damage.

Shadow Panther. Ugly mutant head.

Tracks. I love the character and fixed the legs but you shouldn't have to fix them and the transformation is a bloody pain.

Dinobot. Those dinosaur hands look terrible.

Earthrise Seekers. Too small.

Grapple/Inferno. Too small.

Siege Skytread. Too small.

 

I'll pick one from each toyline.

Siege: Chromia. So much kibble, ugly alt mode.

Earthrise: Arcee. No need to elaborate, everyone knows her problems.

Kingdom: Warpath. Pointless partsforming, fiddly and annoying transformation.

 

Without a doubt, Earthrise Sunstreaker.

 

I'd like to revise my answer to include this piece of hot garbage. The other cassettes were fine. Even though Rumble and Frenzy were compromised a bit in order to fit into Soundwave's chest, at least they came out OK still. Ravage is just a mess.

 

ER Arcee or Kingdom Scorponok.

 

It depends on the criteria for worst. I think the most _disappointing_ for me was Kingdom Ultra Magnus. I really wanted to buy him and a Powered Convoy recolor but that cab is such an utter disaster. Alot of the Earthrise figures had dumb shortcuts that kept them from being great. Arcee was bad but Elita was less bad due to a much better paint job.

As an overall line, Siege was probably the best. Earthrise had more of my favorite figures but so many that fell far short of where they should have. Kingdom was too much BW/gimmick so I didn't buy enough to really judge.

 

Arcee as everyone mentioned.
Rhinox was a failure and should have just reusued the t30 mold
Cheetor- every other BW figure is a fairly faithful update to the cartoon. And then theres Cheetor who is anything but.

 

Astrotrain. Garbage alt modes. Stuffy, stubby robot mode. Just a total missed opportunity IMO.

Note: my real answer would be every Beast Wars figure because I find their designs to be depressingly ugly across the board. I accept their existence by ignoring them completely. So yeah, Astrotrain. Astrotrain stinks.

Co-sign 100%. That Kingdom UM cab was painfully bad.

 

I was gonna say Tracks but the leg upgrade makes him tolerable. Imma have to mention Arcee because this bxtch was so bad when I gave it to someone for free they ass literally tried to pay me to take it back....

 

tough choice between er arcee and siege apeface for me

 

Those under $10 shields that turned into bots. Then also were attach ramps. Never liked these toys. Sorry don"t remember there assortment name.

 

I had forgotten (probably my brain’s self defense) about Kingdom UM. The only time I transformed him back to truck after opening him was to show my 5-yo. He looked at it. He tried to roll it and released it as soon as he noticed that the cab didn’t turn. Then asked me to turn him back to robot. Didn’t ask about him ever again and I don’t blame him. He keeps playing with ER OP in truck-mode, though.

 

Tracks. I don't transform him because he is both a clear plastic disaster yet to happen and annoying as #@%$!

Ol' Jelly Legs

 

Battle Masters. They (the ramps) were okay, but only a couple really stood out. Those would be Rung, Smashdown, and Slitherfang. Rung is just adorable and looks great, just not the most compelling Transformer. Smashdown is an adorable Minotaur and I love it. To pieces. Slitherfang turns into a mechanical snake, I mean, that sells itself. Soundbarrier and Doublecrosser are incredibly bland and pointless, not to mention, incredibly fragile if you use them the "wrong" way.

 

Siege Red Heat and Stakeout. I wanted to get more of the Micromasters, but those two turned me off to the Siege line's modern take of the subgroup. Haven't looked back since and I doubt I'm missing out on much.

 

Re-purchasing characters that I had just bought a year or two earlier just to get a more classic altmode. That was the worst part for me.