faithful, loyal
The dog is a loyal animal.
Al menos siempre le eres fiel a la música.
At least you are always true to the music.
— El médico de Budapest (2020)
Dice que siempre le ha sido fiel a su esposa.
He says he has always been faithful to his wife.
Ham, ama a una buena chica que te sea fiel.
Ham, love a good girl who will be faithful to you.
— La increíble historia de David Copperfield (2019)
El perro seguía a su amo por todas partes como una sombra fiel.
The dog followed his master everywhere like a faithful shadow.
Sí, cielo, siempre te soy fiel a mi manera.
Yes, darling, I am always faithful to you in my own way.