I'm honestly pretty miffed on August's defeat here. I loved the twist last chapter and was really looking forward to seeing how it would affect the fight, but this felt ridiculously anticlimactic and rushed, and didn't account for the inconsistencies that needed to be fixed due to the twist (which I don't think were unreasonable to expect). August showed no sign of... well anything when he first met Mavis back when the 12 reunited (despite her clearly being in an awful situation), and his character was horribly inconsistent - he jumped from being a wise man giving out advice and philosophy, to a sadistic destructive maniac that wanted to destroy everything, to a very confused man with severe mummy and daddy issues. His character transformation could have made sense if it was more subtle, but it was incredibly drastic and all over the place, which doesn't make much sense for a wise ~100 year old man who is clearly very set in his ways. If he had properly met Mavis and slowly transformed into the completed character arc August we got this chapter, then this would have felt a lot more natural, but what we got felt like Mashima just wanted to get this over and done with ASAP. Not to mention this feels incredibly uninspired after we got an extremely similar outcome from a fight just 10 chapters ago - having a recurring theme of tragic familial bonds for this section of the arc is an awesome idea, but you can't have both subplots resolved in a ridiculously quick time period through poorly foreshadowed suicide.
Also a little confused on what Mashima was trying to do here - last chapter we had Precht say August had a magic routed in neither darkness nor light, then this chapter we had a flashback to the panel where August told Jellal that his magic was of light. Ignoring the fact that this is pseudo-philosophy at best and has no relevance to anything (unless we really stretch it and say that the absence of love is connected to the absence of both light and darkness because Mavis and Zeref have a light vs. shadow thing going on), it's quite puzzling that Mashima flashbacked to an inconsistent panel that contradicted what he stated in the previous chapter.
Anyway, aside from my gripes on August, Larcade's demise was really really REALLY tragic. I hated him back when he was relevant 20 chapters ago (and I still find his personality obnoxious), but this made me feel genuinely bad for him. He was honoured that Zeref considered him to be so close to him by naming him Dragneel, and did everything to please his father figure - and what did he get? Killed by his own father figure. Now that's pretty messed up. Still confused at how he was supposed to be a secret weapon for Acno, but... I guess we're supposed to pretend that was never stated? Not that I'm complaining, it became a ridiculous idea once 508 became a thing.
Finally the Natsu and Zeref conflict was pretty enjoyable as usual. Not really sure what Natsu expects from Zeref here considering how the curse works, which kinda reinforces my complaints on Zeref as a villain - if Zeref never had a curse and was acting this way out of his own free will (for whatever twisted reasons), then Natsu's words here would carry a lot of weight, rather than making us go "Um Natsu, you do understand how the curse works right?". But ignoring that, it was both cool and tragic seeing Natsu and Zeref throw away their connection as brothers, and become true enemies. Now that this fight is the main focus (I doubt Acno will appear for at least a couple more chapters) we should see a lot more of this, which is exciting. Plus I'm getting the feeling that the Natsu/END we know isn't Zeref's actual brother - more like Zeref's best attempt at creating a demon in his brother's image. Now that would be heartbreaking.
Oh and it looks like Mavis' plan will involve severing Natsu's connection to the book and Zeref through... the power of friendship and love? Works for me, but not impressed if this is going to be her ultimate plan this arc... not that any of her ''''''''''''''tactics'''''''''''''' this arc were anything to make note of anyway.