I purchased a lego haunted house online to put away for investment purposes, but it arrived with a corner of the box damaged and a crease down one side. I already owned a haunted house which box is in perfect condition that I built and displayed. Should I transfer the contents of the damaged box to the better box? Or leave as is in the damaged box with seals intact? Which way would I receive a better resale value?

I could be wrong here, but my instinct says that new in box is always going to win out over opened box. Keep in mind that a lot of the people who are paying secondary market prices are just looking to get their hands on the set to open and build it. By that point, they don't care about box condition. As long as you are honest up front about the condition, you shouldn't have any problems. If you have the space, maybe keep the mint box and offer it to your buyer as an option. It's always going to be difficult to predict what people will want. Once you open that damaged box, you now have two opened boxes, and none sealed.

While we are all for profit, doing something immoral could come back to bite you in another way.

While we are all for profit, doing something immoral could come back to bite you in another way.

Thoughts on the subjective nature of morals aside, the op did not mention any underhanded tactics whatsoever.

The box in better condition, with sealed inner bags, is worth more IMO. Seals can be tampered with, removed and replaced. There is no guarantee a "sealed" set is actually sealed. There are more and more investors that want to know what the contents are in their LEGO boxes, so unsealed boxes are acceptable to more and more buyers. There are many scammers removing minifigures and swapping out bags from lesser sets, so an opened box in "new" condition with sealed contents that are accounted for might soon become the preferable condition.

I apologize as that is my mistake. I don't know why I read it as OP returning the damaged box back to the retailer.