I think Hades is not the same as Hell. Hades is where all the dead go in Greek Mythology. Hell is where only sinners go to be tortured for eternity in modern Christianity.
Yup. In Greek mythology the underworld is split into different parts. There's a part where heroes go, a part where average people wander around for eternity, Tartarus where the titans are held and then there's a part where people are published. I think Sisyphus is punished in the underworld but I could be misremembering.
Is Christianity the only religion where The dead are tortured and punished forever? Most religions it's more like a purgatory or some whole other realm
Hades - as per Odyssey - is a cold and barren place, no place for anyone to want to go to. So, while, tortured, no, it's no fun.
But EVERY religion, devised as system of ethics where morals don't work, needs to threaten a punishment for people who break the rules in life. Otherwise it doesn't really work as a deterrent.