Enemy Level and Kill XP. Alphas Gives x10 XP.

Party Pals lower level than the player get an xp bonus, up to ~x3.6 Bonus XP if much lower level.

XP Gained from defeating Tower Bosses.
Tower bosses grant x30 to EXP.
Hard Mode Tower bosses are level 55, except for Bjorn who is level 60.

Bonus XP from the first 12 catches of each pal.
At 5 catches it skips 2 steps.
At 10 catches it skips 3 steps.
This gives 17 steps per 12/12 catch you complete.
Catch Bonus alone gives enough xp to get to level 60 at 176 12/12 pals, with 0 other XP sources.

There are 4000 rows in this table, go by the pages at the bottom.