In the purest sense of the word "cathartic," absolutely 86. There's nothing - literally nothing, in any media - that's ever touched me the way the last episode of that series does.
Honorable mentions:
In a similar sense, Akudama Drive. It's especially rewarding because with the vividly over-the-top beginning, it doesn't feel like that's the way it's headed, but it is.
In a milder sense, Honey Lemon Soda. There's just something about that series - to me, it's far better and more satisfying than any of its better-known rivals.
In a similar vein to that, Words Bubble Up Like Soda Pop, which as a bonus is visually stunning too.
In a somewhat different sense, the original OVA of Little Witch Academia. It just sweeps me up from the very first frame and doesn't let go until the last.
And in the more traditional sense, say what you might about the series as a whole, but Sword Art Online S01E03 - The Red-nosed Reindeer - is beautifully touching, as is the entire Mother's Rosario arc.
Sincerity - the characters are essentially honest about their feelings. They might be confused or insecure or reserved or even terrified, but they're not dishonest.
Consideration - in the end, no matter how frightened or doubtful or awkward they might feel, the other person matters most. Though it's not an anime (yet), that's the thing I like most about Only I Know and the MMC Waku. He goes through all of those standard panicky reactions - the doubt and insecurity and questioning and fear - and then he steels his resolve, and does whatever he thinks will be best for the FMC Oura, because her well-being matters most to him
Growth - the characters can't be perfectly attuned and matched right from the start or there's no story. They have to grow into their roles, and if they don't, then there's still no story (though it takes much longer). One of my favorite moments in Honey Lemon Soda is when Serina - the MMC Kai's ex who's introduced as a potential rival - remarks that the biggest difference between her and the FMC Uka is that being with Kai made her weaker, but it makes Uka stronger.
Genuine problems with genuine solutions - similar to the need for character growth, there must be problems along the way that they have to, and do, overcome. All I ask is that they be genuine problems that those people might genuinely face - not asinine contrivances that just happen because that's the way some dumbass wrote it - and that they be realistically settled through sincere efforts - not just deus ex machina'ed out of existence after the drama has been judged to have gone on long enough.
It strikes me that I've sort of drifted away from "themes"....