Hello, is it possible to obtain a evil cohort of the same level as himself with :
Greater Leadership (Ex)
At 2nd level, a noble scion gains the Leadership feat as a bonus feat. He can recruit a cohort up to one level lower than himself. At 10th level, he can recruit a cohort of the same level as himself.
Wicked Leader :
You gain a +1 trait bonus on Charisma checks against evil creatures. If you select the Leadership feat or the Vile Leadership feat (see page 14) at any point when you meet the prerequisites for that feat, you can recruit a cohort who is up to 1 level lower than you (instead of the normal requirement that your cohort must be 2 or more levels lower than you are) as long as your cohort is evil.
If you're a level 10 Scion, sure.
Otherwise no : both the feat and the trait allow the cohort to be up to one level lower than you, neither gives it a free level on top of his maximum.
They do the same thing, which just means your cohort has two reasons to be only one level lower than you.
They don't stack.
Which is a good thing, otherwise you'd end up, at Scion lv 10, with potentially 2 cohorts one level above your own.
That is one strong trait, though.