Some of the most toxic foods for cats include onions & garlic, raw eggs & meat, chocolate, alcohol, grapes, and raisins. Onions, garlic, shallots, and scallions can cause damage to your cat’s red blood cells and lead to anemia. These foods are typically poisonous when eaten in large quantities, but exposure to concentrated forms of onion or garlic, such as onion soup mix or garlic powder, can also be toxic.

Source: Hill's Pet