@lionfromnorth killing him could be much worse for MC. Beating that noble up keeps him scared and less likely to retaliate. Kill him and the capital may go after him and his family
No witnesses? Did this dude mean the MC should kill everyone in the crowded market? If not, I'm pretty sure there's gonna be witnesses. Considering the less than strictly legal nature of the businesses there, perhaps not any witnesses that will immediately report anything... but certainly witnesses that would sell information to a wealthy buyer. Or even just brownnose the nobles and their servants who come to investigate the missing noble for some other sort of potential gains.