I know there's been a lot of contention regarding how Aizen has been portrayed in the anime. With it making him more emotional and seemingly less stoic and in control. He looks more (for a lack of of a better word) vulnerable than he did in the manga and previous anime.
Which has caused a lot of fans who viewed Aizen as this emotionally invulnerable character that can never express anything true and is always walled off to feel discontent with how he's being depicted.
But I personally like the anime's take way more.
Let me explain: Aizen has been in a sensory depravation cell for more than 2 years completely restrained and lacking any human contact. For those who don't know sensory depravation and isolation are torture methods, which means Aizen has been essentially tortured none stop for 2+ years at this point.
Arrogant asshole or not that is bound to take a toll, a heavy one at that. It never made any sense to me how Aizen seems perfectly fine in the manga after what is basically physchological torture.
His more reserved and tense personally fits so much better in my opinion. He is still the asshole we all know and love but his time in muken has affected him.
I know we all joke (specially in the Bleach subreddit) about Adnyeus regretting siring Yhwach and how he is ashamed of him.
But I don't think it is all a joke, because a father that loved his child would never create a new world and then make it so his child would have to kill other people in order to live. Would have never intentionally create a world where his child and his people did not belong, did not fit in.
No loving parent would abandon their child in a completely new world with such alien concept as death all alone with no explanation.
Adnyeus had the power and knowledge to chose differently, but he didn't and really what does that say about him?
Yhwach grew in a world with no death but then was suddenly and forcefully de aged, had all of his senses stolen from him and had to come to the realization that he now needed to kill (a completely new concept to him) in order to survive.
I don't think Yhwach was born evil or delusional, but that everything he went through, everything he saw and experienced changed him.
And even after everything Yhwach still held some love for his father even if it was burried deep beneath several layers of hate and resentment.
Yhwach is in my opinion completely justified in having beef with his dad (doesn't justify the mass murder of countless souls though).
Conclusion Yhwach has daddy issues.