Accidenrly deleted game

If this is for the 360, you would redownload the game from your download history - http://support.xbox.com/en-US/xbox-360/store/redownload-content

If this is for the One, the game would be listed as Ready to Install in your games and apps, you would redownload it there.

Your game saves are saved in the cloud, so no worries there.

I had a similar problem with Ark the other day, I download a 30GB update to get me ready for the Xbox One X, lo and behold I had to re-download the exact same file one day later. now it could be that it was two separate updates, but I doubt it. normally
when something like this happens Wild Card mentions it on twitter.

On the right of your dash click on "system",then storage,pick the device that the items are stored on,like your hard drive & you can delete them from there.

Other option is to just leave it and have whatever achievements count towards your gamerscore. This is support forum and most of us are just gamers like you so there isnt anyway to get into your account.

Actually, you don't have to repurchase all the items. DLC is licensed to both the gamertag and the console it was first downloaded to. This means that any gamertag can access your DLC from the same console. This does not include avatar items.