Let's think about just a few;
1. When he creates a land that can only be happy when run by humans, but doesn't put any humans into the land itself.
2. When he decides to give pretty much every animal in that world the power of speech, other than mice, and gives no explanation at all as to what he has against mice.
3. When the mice finally can talk (only after cutting him down from the sacrificial rock -EVEN THOUGH HE DOESN'T EVEN THINK THEM WORTHY OF SPEECH) and they then save all of Narnia by turning the tide of the battle and Reepicheep then asks for one simple favor and Aslan is like "Nope! That would be pride!" And then only grudgingly grants the favor when he realizes all of Narnia is starting to think he's a total dickweed.
4. When he lets Reepicheep walk off to certain death at the end of The Voyage Of The Dawn Treader.
5. Every time he could have provided useful advice that would have saved the lives of thousands but instead spoke in unfathomable riddles that even Nostradamus would have found ridiculous.
6. When he lets the kids grow up to adulthood as kings and queens and then sends them back to Earth as small children again. Can you imagine the fucking torture of having to go to fourth grade after you've ruled a kingdom, had lovers and done all sorts of adult shit. It's a fucking nightmare scenario.
7. When he kills all of Susan's family at once.
8. When he banishes Susan from Narnia for wearing lipstick.
9. Ok. Fuck it. Everything he does to Susan because he's a patriarchal dickfart.
10. When he kills every living thing in Narnia simply because one moron decided to dress up like him.
11. When he brings Peter and company back to Narnia - as children instead of the adults they were - and shows them how he let the castle they used to rule crumble into ruins.
12. The hundreds of years he lets Narnia be ruled by asswipes before he decides to bring the kids back again.