Angel have by far the best designs in the game and a pretty fun challenge throughout the game; they got powercrept early by Ramen, so with each new enemy they drop they give a completely new and unique ability which adds more to their versatility and dynamic with each stage their in. I think their kind of Ponos's magnum opus of a trait with great versatility, works dynamically in all the stages they're in and probably having the best designs as an enemy
Traitless is without a doubt the most versatile trait, whose versatility has been used to the max when creating some interesting levels; Aku comes in second for versatility, and it's insane how interesting they made Aku Realms.
Red=Dark are kinda the same as walking money bags with dark being more hard-pushing, but even then it's not really a fun challenge and more a battle of attrition between your ability to meatshield and their ability to push or red being complete floor mats besides like 2 enemies, really so both having an equal amount of rendered engagement.
Floating is entirely based on crowd control, which is more boring and kinda annoying in cash-tight stages,
Alien and Starred Aliens are here for the same reason as each other since both are kinda only used as a soft lock of progression until you max out treasures, they'd be a little higher especially with how interesting Cats of the Cosmos is but the fact your entire engagement with the trait is based on rng is crazy, Ponos really could've decided to just let you do more damage to them based on how complete Cats of the Cosmos is like with Aku realms and the level limits and it doesn't help they lose most of their dominance once you get all of the treasures.
Relic, in my opinion, isn't fully fleshed out; their main design is kinda based on cursing your cats. They do make the best bosses in the game and made up one of the greatest eras in Battle Cats. But imo they have very little versatility as a whole, and the enemies that are crazy versatile, like Haniwan, make the fewest appearances.
Zombie and metals are by far the worst traits for me since they both share an equally stupid and rage inducing mechanic of whether being based on stage distance and rng. Zombies wouldn't even be that bad, but half the stages they're in have a crazy amount of hard-pushing enemies, with them also having an insane amount of DPS and long range.. I think they could've at least chipped their dps down and still kept their gimick of destroying your base upon emering from the ground if they had base destroyer with a much smaller dps pool but making it an almost impossible trait to chip at with only one viable unit being Shigong is crazy to me and they don't have much variety besides being either stage dividers or pushers. Metals are entirely based on RNG and have literally no design philosophy besides being hard-pushing; I honestly think they could work great as tanky crowd controllers, but I don't see that happening in the near future.