Negative scoring is a tricky topic, especially if you have them on delays, or non activity - the negative score can compound quickly and you can have someone take a positive, MQL type activity, but due to the engative scoring still not trigger.
If you are using negative scoring, consider some campaigns that can neutralize the negative score from time to time if they are still fresh.
You may also consider doing custom scoring fields for negative scoring based up campaign streams so you are up and down within a stream not entire score.