In volume 1/Episode 9, when Klein asks Asuna to take care of Kirito. It's played for laughs in the LN, but is heartwarming in the anime.
Chapter 19 when we finally get to see the story behind Asuna and her actions with Kirito and damn is it full of fluff from their accidental meeting and to their in-game marriage.
Last parts of Chapter 15 and up until 16 and its aww.
In the Volume 2 story Red-nosed Reindeer, Kirito intends to solo a level boss to get a resurrection item to revive the dead Sacchi, but is slipping deeper into a Death Seeker phase. Klein shows up, with the rest of his guild in tow, and begs Kirito to party with them and challenge the boss together, because Klein is afraid he'll die if he tries to solo the boss. When a PK-happy guild shows up, 30 men strong, Klein leads Furinkazan's 10 man guild to Hold the Line and give Kirito a chance to beat the boss.
After the boss is defeated, and Kirito learns the resurrection item won't work for Sachi, he gives it to Klein.
After that, during the Christmas of the first year in Sword Art Online Sacchi's recorded message for Kirito.
Egil's wife kept his cafe running, and waited patiently for him to come back to her. He did.
The entire chapter/episode focusing on Kirito helping Silica revive her pet dragon Pina is just filled to the brim with this.
In Volume 7, overlapping with Awesome: Kirito and Klein arrive to Hold the Line against a rival guild, so that the Sleeping Knights and Asuna can challenge the level boss.
In Volume 7, Ill Girl Yuuki logs into ALO one last time as she's dying, to say goodbye to her friends. And then the leaders of the main factions of ALO perform a fly-past with their members. Over ONE THOUSAND ALO players from different factions put aside their differences to give her a send off.
Beyond that about a hundred players come to her real world funeral, surprising her remaining family who thought she had no friends.
You underestimate, it was TWO HUNDRED players who showed up.
Volume 4's denoument. Kirito and Lyfa dancing together in the sky, and coming to terms with their emotional baggage.
For the anime, the end of Episode 10 where Kirito asks Asuna to marry him is chock full of this, and has a very powerful When She Smiles moment.
Episode 14, where Kirito and Asuna finally tell each other their real names. And when Kirito wakes up in the hospital, weak from two years on life support, he immediately gets up to find Asuna.
The last twenty or so minutes of episode 25, so much.
In Volume 9, we get this from Eugeo: “Whe-When we were young…we promised…me, Kirito…and Alice, from the day we were born together, to the time we die together…this time, I must definitely…protect…I must…”
A small but meaningful detail: In Episode 1 of the anime, there's a scene of a G.I.R.L. and a young looking man revealed to be a skinny man and a stout somewhat older man when Kayaba resets all the player avatars to reflect their true real-world selves. A few episodes later, they're seen talking together. At the end of the Aincrad arc, there's a brief scene in a hospital where these two men reunite as bros in the real world with much happiness, to the surprise of the hospital staff. Well, they didn't find love per se, but a close friendship is fine too.