Necromunda: Underhive Wars

This will come rather quickly from natural play, however if you want to speed it up:

You can have unlimited funds by hiring and firing leaders and selling their equipment, discounts on hiring from the training hall and bonuses from influence, for sale price at the shop and another hiring discount, will speed this up. Simple then Purchase a fighter with experience (a champion will cap at at level IX for example) and level them up to unlock this.