Worst coaster you've ever been on

5. Manhattan Express - NYNY Casino
Just a really boring layout with uncomfortable trains and roughness.
4. Canyon Blaster - Adventuredome
Again, an unoriginal layout with old arrow trains and head trauma.
3. Green Lantern/Chang - Six Flags Great Adventure
This is at my home park and I can't stand it (pardon the pun) anymore. Really really really rough. It has a good layout for a sitdown coaster however.
2. Apocolypse/Iron Wolf - Six Flags America
I really really don't like stand up coasters.
Honorable mention: The Dark Knight Coaster - Six Flags Great Adventure (and other parks)
I really don't like Wild Mouses, but it's the cheesy pre-show that does it for me.
1. Mind Eraser - Six Flags America (and other parks)
The name gives it away.

Son of Beast at Kings Island. I exited the coaster with bleeding knuckles.

1st: Mind Eraser @ Elitch Gardens. The Headbanging capital of the world.
2nd: Ghostrider (Pre-Refurb) @ Knotts. Brutally Violent.
3rd: Jaguar @ Knotts. My restraint opened on this ride, which made me hate it even more. Jerky transitions, bad rattle, and just meh

Honorable Mention: Vortex @ California's Great America. The Iron Wolf of the West Coast.

Old Ghostrider at Knotts.

I will also say that Shockwave was not very fun either at Great America.

1. Zonga SFDK.
2. Psyclone SFMM.
3. The Demon CGA.

Predator at Darien Lakes.
Hurler at King's Dominion.
Georgia Cyclone at SFOG.
Desperado at Buffalo Bill's.
Canyon Blaster at Circus Circus.
Viper at SFMM.
Colossus (pre-refurb).
Viper at Darien Lakes.
Zyklon at Magic Springs.
Mind Eraser at SFNE.
Shockwave/Batman the Escape at SFAstroworld.
Boardwalk Bullet at Kemah Boardwalk....not prepared for that sudden jerk at the bottom of the hill, got severe whiplash that lasted for over 2 weeks after that...other than that, smooth ride.
Riddler's Revenge at SFFM only b/c IMO it's a bit long. I got bored halfway thru.

That's all that comes to mind at this time.

Excluding kiddie/family coasters as it is a bit unfair to include them, my bottom five are...

5. Bat at Canada's Wonderland (the worst Vekoma Boomerang I've been on)
4. Mean Streak at Cedar Point (very dull and boring, not to mention a bit rough)
3. Steamin' Demon at Great Escape (rough, super short, and just very dated)
2. Shockwave at Kings Dominion (the most painful coaster I've ever ridden...I'm glad it is defunct)
1. Indiana Jones et le Temple du Peril at Disneyland Paris (the coaster itself is ok, but the overall attraction was a major disappointment and easily feels like the cheapest attraction at Disneyland Paris (well, in Disneyland Park at least)).

Honorable mentions go to any other rough Vekoma coasters (I don't mind a smoother Vekoma, but some of the rough installations are pretty bad) and any of the looping carnival coasters (non-looping carnival coasters, on the other hand, are usually okay).

I rode Cobra (Intamin standup), Super Manège (Vekoma looper), and Ednór (Vekoma SLC) yesterday at La Ronde and they all make it onto my list somewhere.

Boomerang at Knott's is trash. It's super rough and could totally be replaced with a much better ride.

In response to AJ- Why did you think Indiana Jones was so bad? When I rode it it was rough but really bearable and it had some fun moments and some decent theming.

Juan, objectively it probably wasn't that bad, but it is in the top five most disappointing theme park attractions I've experienced. The coaster itself was just okay...it wasn't overly rough, but it was uncomfortable, very short, and not all that exciting when you've been on 350+ coasters. Theming-wise, I am probably spoiled by having Indiana Jones Adventure locally, but it just didn't feel up to par for Disney and felt like something I'd expect to see at a regional theme park, plus any Indiana Jones references were minimal. If I did this list purely based on the roller coaster element, it would not be on my bottom five, but per the initial post I took the whole ride experience into account. I'll definitely give it another try and reevaluate it if I get back to Disneyland Paris...perhaps it will be more enjoyable when you're not riding during a rainstorm.

If you want my list for pure coaster quality, remove Indiana Jones and add Looping Thunder at Oaks Amusement Park to the top. That's a pretty good example of a looping carnival coaster and is pretty representative of them all.

4. Kong SFDK.
5. Sidewinder Elitch's.
6. Wind Jammer Knott's.
7. Any Boomerang.

Timber Wolf at Worlds of Fun. Worst Dinn Corp woodie still standing. Not even RMC can save it - this ride just needs to be razed.

The worst coaster I've ever been on was "10 Inversion Coaster" at Chimelong Paradise in Guangzhou, China. The primary reason is because after the first inversion, I was afraid I'd become injured. It was painful, and I kept thinking "I only need to avoid injury 9 more time! I only need to avoid injury 8 more times!"

The second reason is because there was no theming. I mean zero. The name of the roller coaster is "10 Inversion Coaster" for crying out loud!

The next worst would be Son of Beast, as James K said. Terrible.

Funny....there are two votes for Sidewinder at Elitch Gardens...which I believe is the only coaster worth riding there....

My vote is for Mean Streak...it is pretty evil....but there is good news in the future for it.....if you ever want to ride Mean Streak again, do it before September.

The Rattler at SFFT was pretty bad before RMC fixed it.

All Vekoma SLC coasters should be melted down into urinals. I can't think of a fate worse than that for the Vekoma boomerangs...maybe melted down to make boy band earrings for tweens?

Boomarang La Ronde... Owowowowowowow...

Grizzly at CGA has been awful from the beginning. I worked there the year it opened, so I know this to be true. Three that really deteriorated from my first rides are Manhattan Express, Psychlone at 6FMM, and Ghostrider that I hope to love again.