Halo 1's entire campaign is the same thing played through twice but you go the other way and it has Flood.
Not that I care too much because I have had more fun playing that than most other games ever.
I find it quite funny how even for the levels that don’t have duplicates, you essentially have to back track or repeat a large amount of it.
Pillar of Autumn - The Maw
Truth and Reconciliation - Keyes
Assault on the Control Room - Two Betrayals
Silent Cartographer - loop around the island multiple times, go down and back up the command center
343 Guilty Spark - go in and then back out of the compound (it’s own mirrored level)
The Library - self explanatory how repetitive it is
Halo is the only level that doesn’t really fit the mold. I guess you have to save 4 lots of marines but they are in all different areas.