"Itu hanya pendapat dia saja."

Translation: That is only his opinion.

[JamesTWils]

Why both hanya and saja?

[Rick392366]

Why both hanya and saja?

Yes it's double.
It's for extra emphasis that it's just his opinion, and that it's nothing more than that.

[BetaPavonis]

Gracias por la explicación

[Yin449049]

Why is 'that is his opinion only' not also correct?

[IamJacksSpleen]

Ya, itu hanya pendapat dia kamu, laki laki...