How should I develop my units to defeat a Knight?

Come on, play however you want, train 200 Paladins, take a second Castle, I don't care. The problem isn't with your Paladins, but with getting the right spells and finding the right artifacts in the guilds. For example, if Plague doesn't appear, you're doomed. Today, I was defeated by Demons because that damned guild had that destructive beam. The freaking computer gave me some stupid skills, so in the end, I was completely screwed. And I was clearly winning at the beginning. So, even if I lose, I'll be cursing the stupid computer, not myself. Or the developers who didn't bother to create decent dragons for the Necromancer. So, mish-gun, this is purely a scientific question, and who wins doesn't necessarily mean the game is good.
Are you suggesting I give up on the "match," or am I misunderstanding? Okay, if you mean the game on Friday, let's play on Friday, that is, tomorrow.

Don't tell anyone else about the 200 Paladins, they'll laugh! We've already settled the Castle issue – I won't take it, although I'd like to, I'm a man of my word.
You might be right about the spells, but this is more relevant for Heaven. Imagine if Anti-Magic doesn't appear; then, even 300 Paladins won't help, and it will be pointless to play! As for the skills, we're on equal footing, just like with anyone else, but that's what makes the game skillful – you have to make the most of what you have!
So, we'll make your second Castle a Necromancer Castle for convenience and to increase the chances of getting the magic you need! This isn't an act of goodwill, but a desire to play against a strong opponent and prove to you that the Necromancer, even with an army that is two or three times larger than Heaven's, with all the artifacts and magic, will still lose to Heaven, especially Axel with Anti-Magic. I can't wrap my head around it – you're probably the only one who doubts this!

“So, even if I lose, I'll be cursing the stupid computer, or the developers who didn't bother to create decent dragons for the Necromancer” - that's why I don't even want to play with you, and I think anyone who reads this will think twice before writing something!

No one is talking about the quality of the game! You can't judge based on a single game! For that, you need to play many battles and with different factions!