We'd been slowly migrating from Angular 1.X to React (internally: the Angularpocalypse) for a few years and we'd finally migrated over our last few pages. The result was about 100k lines of JS and Rails code that could be safely deleted in a single PR. It had been such a long slog, though, that we felt the team deserved some catharsis.
We took a team-offsite day to gather on a nearby beach and burn the deleted code. In the interest of not wasting that much paper, we burnt a complete list of the deleted files in super-tiny font on a couple pages. We also each grabbed our least-favorite areas of the codebase to print out, including several dramatic readings. My selection was a section of code from about 4 years prior with a comment like //TODO: replace this asap.
I highly recommend it to anyone facing a long, clearly-delineated migration. Gift your old, shameful code to the flame.