Ok i went to nazir after the find cicero quest and he gave me three new contracts. One is a vendor in whiterun. I dont want to kill him but i also dont want to have this show as a quest i need to complete( on xbox and it on the very top of the list). Thanks

You don't have to be assigned contracts. Just don't talk to him unless necessary.

If you want, reload a save before you were given those contracts.

Anoriath, the vendor you are sent to kill, sells and buys only animal products, mainly meat, and so he is not a particularly useful merchant.

However, his brother runs the Drunken Huntsman, a much more useful fletcher, and you ought to watch your back -- not only may he try to take revenge on you for murdering his brother by hiring thugs, he will dislike you forevermore, and be more likely to hire thugs for other infractions against him.

So theres no way to go back like you can with vex and say i dobt want this or intentionally fail it. I understand hes not useful but the city already has a small population. If theres no option thats ok as i will reload to a save from 2 hours earlier ( only hurts a little)

Does your disposition with a NPC effect your chances of Thug attacks? I've only ever had thugs come after at the very beginning of the game, never anytime after that, even if I steal everything out of an NPC's home!

There is at least one thug encounter -- either the one for murder or for stealing -- that requires that the NPC dislikes you.