How do you when by at least 4000 duel assessment?

How?

Simple. Use a God card. Got over 6000 easily.

I tried achieving 4000 AS with dealing 5000 damage with a single blow, which according to the assessment score description, gives you 1800 additional assessment points. That, added to all the other things I got points for, should've given me a total of 4800 AS. Guess what!? It didn't even register on the assessment list. So I got well below 4000. I've come to realize that most tooltips in Duel Links are so vague that you actually have to try them out in action to know how they really work. That goes for a ton of tooltips, descriptions, effects and even how chain links work. The dilettantism reflected by these poor designs is laughable.

I would recommend building a deck with the winged dragon of ra in it. That'll give you crazy points

Why i can't achieve this mission? I already win using yami yugi with 4000 life point. Need help, please.

I recommend 2 ritual wepon.
Over 5000 damage inflicting can make 1800 point

http://duellinks.gamea.co/c/5agpdwxm

you'll have to look and do the things that give you bonuses like fusion, ritual, tribute, etc. Or just copy any high score deck from the site or anywhere else.