Mimado vs. estragado
While both words can be translated to "spoiled" in English, Portuguese distinguishes clearly between a person's behavior and the physical condition of an item. The choice between mimado and estragado depends entirely on whether you are describing a living being or an inanimate object.
Mimado
B1This word describes a person (often a child) or an animal that is pampered excessively or is overly indulged. It implies an entitled personality or a lack of discipline because they are used to getting everything they want.
O menino chorou no mercado porque é muito mimado.
(The boy cried at the market because he is very spoiled.)
Os avós deixam os netos mimados com tantos presentes.
(The grandparents leave the grandchildren spoiled with so many gifts.)
Ela tem um gato mimado que só dorme em travesseiros de seda.
(She has a spoiled cat that only sleeps on silk pillows.)
Não seja mimado e aceite a decisão do chefe.
(Don't be spoiled and accept the boss's decision.)
Estragado
A2This word refers to something that has gone bad, is rotten, or is physically ruined. It is primarily used for food that is no longer safe to eat, but it can also be used for machines or objects that are broken.
Não beba o leite, acho que ele está estragado.
(Don't drink the milk, I think it is spoiled.)
O cheiro ruim na cozinha vem da fruta estragada.
(The bad smell in the kitchen comes from the spoiled fruit.)
Jogamos fora o bolo porque estava estragado.
(We threw away the cake because it was spoiled.)
O motor do carro está estragado e precisa de conserto.
(The car engine is broken and needs repair.)
Summary
Use mimado when talking about behavior, personality, or pets (meaning pampered/indulged). Use estragado when talking about food, objects, or plans (meaning rotten/broken/ruined).