The tl;dr answer is almost everything.

Let's start with Tattoo- I love the way the episode sets everything up. I've mentioned it in rewatch before but I really want to explore the use of the word "ephemeral" in Tattoo. From exploring Scott's break up with Allison, to his tattoo not lasting, to the way he uses the word, even to the idea that Scott's status as a beta is ephemeral, even at this point in the series. I love the scene with Stiles and Derek holding Scott down to blowtorch his arm. I LOVE the way it opens with fucking BRAEDEN rescuing Isaac on a motorcycle.

I love the introduction of Deucalion. I love and adore the meet-cute in the elevator. Please enjoy @spikeface's brilliant fic: a certain potential for a fascinating glimpse of Deucalion's POV in that scene.

I love that Scott is Isaac's werewolf contact. I love the tension as the alpha pack stalks Braeden (I would be mad about how this ended, except she comes back) and their intro. I love the tension between Allison, Lydia, and Derek. It's a very well-done episode and definitely sets up a fantastic season so well.

Chaos Rising introduces Heather, who is friends with Danielle from Party Guessed. I was excited. We get the vault rescue, and there's some fun Steter banter. "No, you idiot, I live in a condo downtown, will forever be a favorite moment. The vault rescue! Scott's look at the end is A FAVORED moment, the blood on the chin? I cannot.

Then, we move on to Fireflies. I am weak for Scott saving those kids in the beginning, for the tension between him and Allison, and for the introduction of Cora! And then they are working with Chris. Who is still pointing a gun at Scott, but Scott is so soft and accepting of it. "I get that," he says. 🥺 Then they do a rescue! And Jennifer is there! And Derek is so worried about hurting her. Unfortunate. (When I was first watching, I leaned over to @illbeintheend and was like, "Tell me she's evil?" :D ) I think my favorite bit of Unleashed is when they pull the motorcycle swap on the twins. That is like PEAK supernatural teenager shenanigans to me. And they deserved more lower stakes (not that the twins are entirely low-stakes) shenans, overall. I also LOVE LOVE LOVE that Allison knows so much about motorcycles. Scallison motorcycle trip whenst?

Frayed. Frayed. FRAYED. BELOVED. I love so much about this episode. The sciles! the scallison! more truedemon in the elevator? and then on an escalator!! the scerek! the scisaac! BOYDDD. That moment where Scott is like "Well, I do," when Boyd doesn't care what happens to himself? Gyahhh. I CANNOT. And the the fight scene? Is SO good? Despite them having forgotten about light bulbs by 3a I find that to be one of the best choreographed fight scenes in the show. The Coach of it all? Ofc he's not gonna let them stop for a bathroom break, SIT DOWN BILINSKI. I love Frayed. AND THEN WE GET MOTEL CALIFORNIA RIGHT AFTER?? Lydia's arc in this is SOOO good. The Allison and Lydia moment where Allison is just "I believe you" and Lydia is so touched and clearly bolstered, it's one of the reasons I head canon she's had access to her powers her entire life. It's just now that people believe her about them. The Isaac and Ethan character moments? LEARNING ABOUT ALICIA (GREAT BUT OMG SHOOOOWWWW WHY IS THIS ALL WE GET???). Boyd. Cry!!! And THEN. The angst of the parking light scene at the end. I tear up still watching it. (Tbf I cry real easy.) Currents. I love Currents for the metronome scene and the way it highlights Boyd's intelligence. He has one of the best plans. And then the way it ends? That hurts me. Proto-alpha Scott almost rescuing Deaton? Bbbb. I have mixed feelings about Visionary. The Paige arc is devastating. Read my own excellent fic (i just) died in your arms for a look at my thoughts on her and Derek. I love the glimpse of pre-canon and Deucalion's backstory. I find the "unreliable narrator" bit to be a touch heavy-handed, but it's grown on me after many watched for fics.

The Girl Who Knew Too Much and The Overlooked. GYHAHHHH! I love so much about these. The scydia hand hold moment. "For someone like you to help" she says to Scott and I MELT. The big orchestra crescendo! The death of Deputy Tara and the little hints at her relationship with Stiles? The way Derek absolutely believes Scott and Stiles about Jennifer and her utter shock but quick turnaround?

The elevator scene! It's so silly and SO GREAT. I love it so much, okay. Deucalion manipulating events? The desperation as Stiles and Scott try and rescue their parents? Listen, these episodes are also so good. And then we have Scott going with Deucalion at the end of the episode. The way he has no idea what to do. He's just a lost kid, in so far over his head. And his mom and Stile's dad are missing and his (pretty damn good, too) English teacher is evil and there is Deucalion. And he has no choice and maybe he was right in that motel parking lot, it certainly feels like there's no help.

Then Alpha Pact happens. Then we get to Lunar Eclipse. And I just. The ice baths?? I have spent so much time wondering how Deaton, Isaac, and Lydia felt sitting there. Waiting. For hours. Lydia desperately holding back her screams for Allison, Scott and Stiles. Also, they all look so gooood in black. The Nemeton! The matching tattoos! The way it brings everything together to s1. The scalisaac moment with Rafael? Priceless. Love Kalia and Jennifer's showdown. It looks so cool, first of all. But there is a moment, where you think, just maybe Kali might NOT double down. And then the glass shards fly.

The bit where Deucalion is "brother against brother, how very American," cracks me up, every watch. And then he roars and tries to force Scott to kill and well, then we have an Eclipse. AND THEN AND THEN AND THEN we get the true alpha moment we've been building to since Scott threw off Peter's control in s1 and chose his own pack over Derek's in s2. That moment is so good.

Thank you for asking, anon. <3 I just love 3a so much.