The following monster types grant too much experience and hit the int31 max (int32 signed data type used) and overflow in the right way where the party bonus added to the total experience (after the champion/unique and player count bonus) will become negative and completely cancel out the total experience given, causing monsters to give 1 experience.
The monsters capable of doing this are those with base monster experience (before champion/unique bonus, but after MonLvl (monlvl.txt) * Exp(H) (monstats.txt)) higher than roughly 153201, or 766002 with the unique bonus (x5) (this may be incorrect, but does not matter, as no monsters come close to this line. All monsters are significantly lower or higher than this (outside the margin of possible error)).
The following monsters have this issue:
Oblivion Knight in Furnace of Pain (dkmag3)
Horadrim Ancient in Sewers (Act 3) Level 1 and Level 2 (unraveler4)
Unraveler (Achmel the Cursed group) in Throne of Destruction (unraveler5)
Unraveler in Pit of Acheron (unraveler7)
Horadrim Ancient in Worldstone Keep Level 2 (unraveler8)
Horadrim Ancient in Throne of Destruction (unraveler9)
Please remember that this is only for 8 player parties (not just players 8 games) while these particular monsters are unique or superunique.
I did not check Act/Uber Bosses, don’t think any of them will overflow and stay negative. Unsure if they will overflow at all.
See my experience calculator (be sure to check pages 3 and 4, those are the most important): https://docs.google.com/spreadsheets/d/1FTrSsBXkgjzljBKQ36Lq4gCYjtmf1hkZ2uxffJPQ9Q0/edit?usp=sharing
This becomes significant because areas containing these monsters are more likely to be farmed with the Terrorization of areas (this bug has always existed, just nobody cared before).