Spring Kinkfest

Tags have sometimes multiplied because people wrote the fandom differently, switched the names in the pairing around, wrote a new tag instead of taking the one that was there, or made a typo.

All the firsts tags could be merged into the seconds:

Devil May Cry

devil may cry (sparda/eva) same as → devil may cry: sparda/eva
devil may cry 3: dante/vergil same as → devil may cry: dante/vergil
devil may cry: vergil/dante same as → devil may cry: dante/vergil

Digital Devil Saga

digital devil sgaga: gale/demi-fiend same as → digital devil saga: gale/demi-fiend
digital devil saga serph/demifiend same as → digital devil saga: serph/demi-fiend
digital devil sage: gale/cielo same as → digital devil saga: gale/cielo
digital devil sage: gale/roland same as → digital devil saga: gale/roland

smt: digital devil saga: argilla/sera should be → digital devil saga: argilla/sera
smt: digital devil saga: naoki/seraph should be → digital devil saga: demi-fiend/seraph

Shin Megami Tensei: Nocturne
This is made difficult by the nameless hero...

smt: nocturne: dante/hitoshura should be → smt: nocturne: dante/demi-fiend
smt: nocturne: hitoshura/futomimi should be → smt: nocturne: demi-fiend/futomimi
smt: nocturne: hitoshura/sakahagi should be → smt: nocturne: demi-fiend/sakahagi
smt: nocturne: isamu/protagonist should be → smt: nocturne: isamu/demi-fiend

There's also a superfluous date tag:
oct 9 same as → october 9

I'm sure if one looked through the big fandoms like FF and Bleach it'd be possible to shave off more tags...