The worst Jewish curse is יִמַּח שְׁמוֹ וְזִכְרוֹ (Yimach shemo ve-zichro -- May his name and his memory be erased). When people die, they go to Gehinnom, where they are judged and punished for their sins. Within a year, they are either allowed into the World to Come (olam haba) or their souls are destroyed forever. The latter is what the curse wishes.
How does that work in practice, in this world? The names and memories of the wicked are not erased. They remain in history books, and even in biblical injunctions to remember them. (Remember Amalek!) Is this discussed anywhere?
Collateral issue asked separately: Is Gehinnom just punishment and judgment followed by verdict: Olam Haba or extinction, or can you do something there yourself (like repent)?