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Pokemon can never be directly lethal - a L100 Hyper Beam to the face will at worst leave you unconscious. This explains why Ash hasn't been killed from Pokemon moves, and why Team Rocket is still alive after a powerful attack hits them square on (though I don't know how they survive the fall).
However, indirect actions, like Razor Leaf cutting a chandelier so it falls, can occasionally be more dangerous. Even though Rocket is a criminal organization, they like their stolen Pokemon alive, so generally don't go for that style of attack.
also I'm a massive vorefag and this lets preds eat their Trainers for fun, then return to their Pokeballs, vanishing from around their prey
Obviously, this theory ignores the manga, like most things.