Tulireki is probably objectively the worst one I have ridden. A coaster of that size ought to deliver some reasonable thrills but it just does nothing, is surprisingly rough, has a poor throughput, and its USP with the tilting cars is barely noticeable.
It must seem even worse by comparison now that it has Taiga wrapped around it.
The roughest I have done by a mile is Montezum but I still enjoyed it.
The only coaster I’ve ridden that I genuinely disliked to the point where I’d never ride it again was probably Turbo (the Pinfari looper on Brighton Pier). I don’t usually mind rough rides (Colossus is genuinely my favourite ride at Thorpe) but that was beyond horrific and nowhere near exciting enough to be worth the pain
Its a tie between Hero at Flamingo Land or Condor at Walibi Holland. being the first SLC constructed its strongly in need of a swift bulldoze, quickly followed by the rest of them. Hero could be made slightly less horrendous by the use of a full body bubble wrap suit.