Blue Magic is never missable. You can miss one of the spells until the very end of the very last dungeon, but nothing missable. You learn Level 5 Death from quite a few enemies like most Blue Magic, but IIRC the easiest way is a Whale Zombie on the shores of areas you could only get to with a boat or a Zombie Dragon or Stroper from the Iifa Tree.
Using the word "lolicon" is A-OK. but if you go and use its less niche synonym, that's going too far. - Norse Mage121.
1. Auto-Life + Limit Globe for EX2PG Challenges 2. LV5 Death for torturing Grand Dragons 3. White Wind for OMFG super-duper-wonderful MT healing 4. Mighty Guard for OMFG super-duper-powerful defense against everything 5. Frog Drop for potentially guaranteed 9999 DMG 24/7