Fanfiction

Comedic endings should be conclusive but still leave you laughing, a wacky one liner is the best way to do so. You can leave it open ended of course, but there are a limited ways to do so without seeming repetitive.

Fluff conclusions don't have to be definite, they can leave the readers imagining how the next few hours went. Either with a romantic partner leading them somewhere else, or a close friend or family member inviting them to somewhere else for more fluffy events is fine. Of course, you can end it definitely with a good 'ol nap or anything really. Conclusions aren't the most important part of this kind of writing (at least to me).

The conclusion depends on how you styled the angst.

RESOLVED

The conclusion should either be happy, as all conflicts are resolved, or bittersweet as some conflicts are resolved. A hopeful ring fits in with more hurt/comfort-based angst, but when it's just hurt/no comfort then bittersweet should be the nicest you get. Pure angst endings are hard hitters and can be used for this, especially if the way the main angst was resolved was particularly brutal, but it's easier to write for the other two in my experience. 

UNRESOLVED

The conclusion should be angsty (even more so), something along the lines of death, cutting ties/self-isolating, or just this deep harrowing sense of sadness/anger. There are about a million ways to take an unresolved angsty work, but concluding one is incredibly difficult because conclusions are the most important part of an angsty work. Whatever the character's emotional/physical state should be brought to terms in the end.

Romance conclusions can be open-ended, ending with a happy finished date, continuing what they were doing previously, and getting married. There are a lot of options. There are specific ones for each type.

• PINING

The conclusion can be the characters getting together, after they get together, or still left in a state of pining. Sometimes you just wanna write a character having it bad for another and nothing else, and that's fine! Benign endings are best for pining-to-pining endings. The early established relationship era has great potential for open-ended conclusions, but sometimes a fluffy end is perfect. Hands down if you're choosing to end things on the characters becoming an item then make it fluff I beg of thee.

• ESTABLISHED

Conclusions for this should more often than not be fluff unless you want it to lead into another installment or want it to imply bad news is incoming. In which case go for cliffhangers that are just unbearably cruel to your readers mostly because their comments are funny as hell. 

• PROBLEMATIC

The conclusion for this can be the end of the relationship (escape from toxic behavior, lifeboat to a sinking ship, admittance that they aren't ready, literally dying because I'd count that), a compromise being met (a promise to change, willing to try, a discussion incoming about certain behaviors), or a resolution to whatever issue there was (bad ending, end of a serious fight, mutual breakup because nobody was happy there.)