If had to delete one single Pokemon from existence out of Unova, it would be Alomomola. Some of my reasons would be:
- It's not a part of an evolutionary line, so nothing would get messed up (even though pairing it up with Luvdisc would have made sense).
- Other than HP, Alomomola's stats aren't really impressive, and just middle of the pack really
- It's pure Water-type, which is hardly unique
- It has a pretty generic moveset compared to similar Pokemon
It really seems like it's just in the games as a filler, because there weren't enough fish-like Pokemon in Unova. Even then, nothing really stands out as unique or special with it, so I'd have no problem if it didn't exist.