RPG Insanity

The best weapons in term of attack power are the Crowley’s weapons which are found in chests in the post game dungeons (2 in Moyu volcano, and 2 in Jili temple).

the second best weapons are the fluffy weapons, which are found in chests in the post game dungeon, the stern bun park.

Other good weapons are the ones obtained from the long term missions rewards:

Star Magic Staff, obtained from collecting 24 runes.
Star Magic saw, obtained by clearing the level 500 meteor gym challenge.
Star magic cannon, obtained by registering 200 types of enemies in the enemy journal.
Star magic sword, obtained by completing all 24 side quests

You can also get great weapons from the forging gatch, since this game is very generous with the points compared to other Kemco games.

Yeah, this game offers a lot of great weapons for very specific purposes. Because of their "inflicted damage +40%" effects, I think the in-game premium shop's ultra-rare weapons (Glamourheim, Mundisarus, Voluptuous, Magna Caritas) are the best allround weapons that you never need to switch out.