In fact WalMart's European arm, ASDA, is heavily unionised and management have a love / hate relationship with it but on the whole put up with it. At one point

In fact WalMart's European arm, ASDA, is heavily unionised and management have a love / hate relationship with it but on the whole put up with it. At one point ASDA management tried to induce workers to waive their right to collective bargaining in return for a pay rise; a court found that unlawful and fined the company and made them compensate the affected workers £2,500. So they have largely buried the hatchet but it is the only place in the world that WalMart tolerates unions.