"This is the reddest dress that I have ever seen."
Translation:Ini gaun termerah yang pernah saya lihat.
Why "Ini gaun termerah yang saya pernah lihat" is wrong?
The word order should be like this :
"Ini gaun termerah yang pernah saya lihat".
In such a 'yang' clause, the clause should be the 'passive type 2' .
That means that nothing comes between the agent/actor ('saya') and the verb ('lihat') .
Here is more info :
Passive type 1 and 2 , Tips & Notes, Addendum.
I have a different opinion from @Rick392366. This sentence is not passive because "saya" was not "seen" by someone. Rick392366's interpretation also cannot explain the counter-argument raised by @Supercoole4.
Here is my humble opinion. The similar question was posted here and I got answers from native speakers. https://forum.duolingo.com/comment/29384726
If the same logic can be applied, both "...YANG PERNAH saya lihat..." and "...YANG SAYA pernah lihat..." are grammatically correct. But the latter means a bit unnatural. "Yang" amplifies the following word. So, the former sentence ("yang + pernah") implies that I have seen many tomatoes in my life. And then, I pick up this tomato and describe that it's the reddest (i.e. emphasizing "ever"). Meanwhile the latter sentence ("yang + saya") implies that other people have never seen but I am the (only) person who can see (i.e. emphasizing "saya"). Therefore, the latter sounds a bit awkward.