In no particular order:
Bandit @Movie Park Germany
This one is infamous for being unbearable rough. The T-Bar restraint makes it even worse, as you keep hitting your thighs when the train whips from side to side.
Several SLCs
Self explanatory. I would like to note, that not all SLCs are what I consider unbearable, but the bad SLCs certainly are. Main culprits: MP-Express/Iron Claw, Limit, Condor. Oh btw, Infusion was one of the best.
Tonnere de Zeus (not the Gravity Group version)
Take the bad from Bandit and crank it up to 11. Pure pain, from the first drop until the final brakerun.
Voltron Nevera powered by Rimac @ Europa Park (outer seat in one of the bad trains)
This ride could be the best in Germany. But if you happen to get a bad train (train 2 is especially bad) and sit on the outer seat, it might as well be Germany's worst.
Cool & Fresh/Migfer @ Wonderland Eurasia
I rode this on the funfair when I was a child, and even then, it was incredibly rough. The brakerun wasn't a brake - it just stopped the train instantly.
Kirnu & Insane @ Linnanmäki/Gröna Lund
I guess all Zac-Spins are as bad as those? Certainly intense rides, but also very unpleasant. Insane is worse, because its longer.
Nitro @ Denlys Parc
A family coaster on the list? Yes. The ride itself is rough in places, but certainly bearable. That is, until it hits THAT spot. There is one spot in a right turn that has a jolt from hell. We both had a headache for 2 days afterwards, as well as neck pain. I was so glad that I had brought some painkillers with me. Horrible
Zamperla Volare
I know it is crazy that such a premium manufacturer could ever produce a horrible ride. But they actually managed to produce maybe the overall worst coaster model ever conceived.