Toyota and Honda have each other as direct competitors. If one of them sacrifices reliability, it's over. There are also second tier ones like Nissan making interchangeable cars, so if say Toyota stoops to Nissan's level, then they have to start selling at Nissan prices.
I would also say Ford, but their reputation for reliability applies only to their trucks.
I would also say Ford, but their reputation for reliability applies only to their trucks.