Sisyphus was punished by the Gods for cheating Death not only once, but twice. When he came to the end of his lifetime, Sisyphus was to be sent to the underworld. He tricked Thanatos into showing him how the chains worked, and then kept him trapped in those chains for many days. Later, he convinced Hades to let him go back to life and promised that he would be back after three days. But he did not come back.
Sisyphus was condemned to be forced to roll an immense boulder up a hill, only to watch it come back to hit him, repeating this action for eternity.
Tantalus invited all the Gods of the Olympus to a feast and dinner. Realizing that he did not have enough food, he killed his son Pelops, cooked him roasting the pieces of his body and served him to the Gods. However, the Gods understood what was going on and refused to eat.
The Gods punished Tantalus for his unforgivable crime. He was made to stand in a pool of water beneath a fruit tree with low branches, with the fruit ever eluding his grasp, and the water always receding before he could take a drink.