This probably just came out wrong, but man...
The thing about Redemption/downfall is that those do a 180 in their alignment. Up to that moment BF mentioned earlier, Sasuke wasn't really Evil. You could call it Chaotic neutral. Neither good or evil, as he just followed his own private motives. Sure he deteriorated more and more. But the moment with Karin was the actual turningpoint in him being Evil.
Which means only now, as he is Evil, has he become storywise able to be redeemed. So anything he did before was, in terms of being able to be redeemed, meaningless.
In other words, his real Evild deeds are still ahead of us.