Board Thread:General Discussion/@comment-30406012-20180212163452/@comment-33589545-20180213182129

Danvirus89 wrote: Negative Symptom, but what will be different this time. Goku was still no match for Jiren last time he used Ultra Instinct. what would be different now? how could it give goku THAT much more power??? it doesnt make sense

So far goku has only mastered the defensive portion of UI. He still hasn't been able to attack properly as his body is needing time to think about it. This has all already been explained, he is basically only fighting at half power in UI up until now. There's the explanation.