Abdul Al-Hazred is your ultimate opponent, which is why he is so difficult. Currently, you will not meet a greater challenge in this mod.
Fighting him may require creativity and some luck.
I myself am curious how others handle it, but as far as I know, some players succeed ;)
Here are my ways:
1) Wars - you are unlikely to stop Al-Hazred in a single war, but a series of wars can gradually devastate his military potential. His special troops do not renew very quickly.
2) Plotting - Abdul has a high resistance to scheming, but using murder intent during an activity is something worth trying.
3) Mage duel - Al-Hazred is a powerful mage, but even he can be unlucky in a duel. Many spells during a duel have a small (or greater) chance of killing the opponent instantly. If you can catch Abdul at a time when he is not highly power saturated, your chances increase significantly. And if you manage to get the Chosen One trait, you can fight him almost as an equal.
4) Pure luck - you can always wait those 500 years until Abdul chokes on his food and dies... ;)

In any case, it won't be easy, but that's what this opponent is all about.

honnestly, the only issue i have with that is that he is starting to conquier like everything, i dont mind taking some fire ball, but he is just ruining my world

He is an archmage who has decided to conquer the world. And he has the right tools to do it. Only you can stop him.
Btw if you find him too challenging an opponent, you can turn him off in the game rules.

If you have the crown artifact, you can counteract his expansion by corrupting his vassals to make them join you instead. That is how I sabotaged his empire before war, and halted his expansion completely. All he had left was barons by the time I finished him off.

One thing that can also potentially help weaken him a bit is he has magic immunity, his vassals and courtiers do not. I spent the first part of my attempts to defeat him slowly driving him into bankruptcy, with the previously mentioned corruption approach combined by dropping plagues and firestorms on his courtiers or barons in his counties, to reduce his income. He seems to still have to pay some amount for all those event troops, so you can pretty effectively drain his income from these two approaches, at least until you kill all those event troops (but then he is a lot easier to beat in a fight).

You might have some luck stressing him to death, I had a few powerful demons die that way. He does seem to be highly resistant to it though, you would need a lot of ways to cause him stress and some luck. Some methods are sending him mocking poems, killing his family members and friends (at least it causes stress to my character, so it probably does the same to him), challenging him to non-lethal duels with stuff like challenge rival to fight, challenge for artifact (or accepting his challenge), taking out your anger if you have the wrath trait, stuff like that. Problem is he seems to generally have 100 prowess and wins any time it gets to sudden death, even if you are both capped at 100 prowess and you have more total prowess than him.

None of this was enough to kill him that way in my game though, at least not before I took him down through other methods.

From my attempts to fight him, I feel that war is probably the easiest way.

Even if you can't fight his army directly, you can avoid it, going around sieging provinces and running whenever his army gets close until eventually you have all the warscore you need. In my experience my armies were always much faster than his and easily able to avoid his forces, though I had a lot of heavily upgraded stables so that likely helped, in addition to having a martial ruler at the time.

You can also get his army to slowly die off from attrition that way, he seems to hate splitting his personally led, special troops army (which makes sense, if he ever did I would take out the ones he let split then run before the rest of his army could stop me. I did the same to his regular armies), so he is always well over the supply limit, and his supplies don't last forever. When I started killing his army through attrition he surrendered the war, so you might want to try not having 100% warscore when you do so.

I eventually defeated his army by stacking my character's combat advantage as much as possible (using two family epics that gave +10 controlled territory advantage, as well as magic artifacts), taking out small bits when he tried splitting (but I think those were just levy troops), and having him join a battle while I was attacking said troops. My army was already winning quite a bit by the time he joined, far outnumbered him, and though this wasn't the plan, it actually used the commander of that smaller stack for combat stack, not him, allowing me to completely wipe his army. If it did use his combat advantage, I think I might have still won, but it would have been much less certain.

:D
The idea of using the crown is brilliant. I will have to limit it somehow in the future ;)

Today I encountered a great demon who specializes in demon hunting. He does not belong to the demon family and has a strategy of 100 points. I cannot defeat him in duels, nor can I use conspiracy assassinations. The powerful enemies have caused the collapse of my empire. Merlin's beard, this demon even has no claim to land, which makes it impossible for me to use war tactics to deal with him as a lord.

I wonder if you are talking about Abraxas, Bael or Astaroth... Although it seems to me that each of them belongs to the Hellish dynasty.

Hey, a small question here. How can I get the Chosen One trait??

@HunkHerrmann
The Chosen One is the source with the maximum magical potential (100). The magical potential is determined at birth, being partly random and partly inherited from the parents - later on the potential may change a little during a lifetime, but only slightly. Mostly it will also not be higher than 85, with one exception, but about that in a moment. The Chosen One is a very powerful trait designed for AI (or rather for one particular NPC) to challenge the player in the late game. The player (and any other character) can only be born a Chosen One if one of the parents is Pandora, the demoness from the prophecy (that's the exception, and there's only a 3% chance of that ;) ). The Ultimate Spell is the only fully repeatable way to increase magical potential, so theoretically using it repeatedly will eventually give you 100 potential. You can also use cheats.

Thank you for your insight on the matter. I remember you once said that the Chosen One trait will be removed in future update. Is that still the case? I hope not, because of how difficult to get it, it is a good roleplay element.

Okay, let's actually clarify this. There used to be a separate Chosen One trait, and it was used in mod. In fact, this trait still exists, but will actually be removed (it is long overdue). It is no longer used and cannot be acquired (apart from the console command), and has no effect on the game mechanics (gives you nothing).
Currently we have new version of 'the Chosen One' which is simply a Source trait that has 100 magical potential, nothing more and nothing less. So if I'm talking about a Chosen One, I'm referring to a Source trait that has 100 potential. This is difficult to get too...

the problem with the magical battle with him is that it doesn't feel like a clash between two great mages (or a great one with someone trying to survive), there's no way to prepare for the battle, and the battle itself doesn't feel like a great ыекшлу, but rather like a game of russian roulette, the one who gets the chance of the ultimate death first wins. that's all. And that turns the battle with him into a game of "die - load - until you win".

@Raksaнутый
Thanks for your insights. This issue is an object of my consideration and I hope to do something about it in the future