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Trimming the roots caused this issue. Likely, the portions of the root (the tip) that take nutrients and water up have all been destroyed. Some plants can recover quickly, but this one will not tolerate root pruning in this fashion.

From here, it will be a race. If the plant can regrow some roots before it dies, completely, then there is a chance that you may save it.

In the future you will want to repot very carefully. Try not to disturb the roots unless you want to divide them up. Even then, be sure to keep them intact while dividing.

This article will help:

https://www.gardeningknowhow.com/houseplants/peace-lily/repotting-peace-lily-plant.htm

It may have been pot bound so what you did was the right thing and should help. Keep them watered and provide bright but indirect light.

https://www.gardeningknowhow.com/houseplants/peace-lily/peace-lily-plants.htm

It will all come down to proper care. Correct watering habits, proper lighting, and occasional feeding will keep this plant alive and happy. They can be quite particular. These articles will help:

https://www.gardeningknowhow.com/houseplants/peace-lily/peace-lily-plants.htm

https://www.gardeningknowhow.com/houseplants/peace-lily

It all comes down to proper care! They can be a bit particular, so, many things can cause browning leaf tips.

In order to keep it at its best, there are some things to know. This collection of articles will help:

https://www.gardeningknowhow.com/houseplants/peace-lily

It, definitely, needs to be repotted! I think that doing so and treating with a fungicide will take care of the issue. Just be sure to give it the best care, possible, and take care not to overwater:

https://www.gardeningknowhow.com/houseplants/peace-lily

It's best not to use garden soil on your houseplants. There are too many organisms in garden soil.

I would repot the plant since you think it's been overwatered. There could be root rot setting in. Wash out the container real well and use fresh potting mix. Check the roots and cut off any brown or black roots or anything mushy. Also the container shouldn't be more than one to two inches wider than the previous pot. Moving to a too-large pot can cause the plant to be overwatered. Here is how to repot:

https://www.gardeningknowhow.com/houseplants/peace-lily/repotting-peace-lily-plant.htm

https://www.gardeningknowhow.com/houseplants/peace-lily/peace-lily-plants.htm