RPG Insanity

im trying to tame everything to get that 100% complete but im wondering if i need to have all 160 pals at the same time or if catching it once and fusing it away will work too, please let me know and thank you in advance

You do not need all 160 at the same time.  One a monster has been a pal, it stays counted, even if you somehow get rid of it (say by fusing it again, etc.).