Not Received Giveaways

You don't need to take any action if you don't want to. The giveaway will just remain in limbo. It will not show as won on your account, but you will not be able to enter other giveaways for that same game because the enter button will say that you previously won the same game. If you want to enter for more giveaways for that game to try to win a copy you can activate, just mark the one you already won as not received.

Marking a giveaway as not received will not have a negative affect on your account. It will just show the game on your profile in the won section with your name in red indicating that you won it, but you did not receive it.

Each winner that marks their win as not received will simply remove 1 giveaway slot from the giveaway creator, they will not get a suspension. If the giveaway creator is reported and support feels like they created a fake giveaway for some reason with no intention of sending the games, then they can get suspended.

If you mark the giveaway as "not received", you will always have the option in the future on your won giveaways page to change the feedback to "received". So, if the giveaway creator logs back into the site in the future and decides to send you the game, you can decide to accept it and mark it as received. Or if you don't want it anymore for some reason like you won it from another giveaway or just changed your mind, you can let them know and ask them to request a new winner.

You don't need to worry about sgtools. A non activated win on sgtools is when you mark the giveaway you won as received, but you do not have the game activated on your Steam account. This is usually when the winner takes the game and regifts, trades, or sells it.

I don't believe you can ask for the giveaway to be deleted. You can give the giveaway creator your permission to delete it if they want to have it deleted, but that would need to be requested by them.

Mark it as not received and leave a comment in the giveaway, that you are happy to change the feedback to received, if the giveaway's creator comes back to Steamgifts and send the proper key/gift.

That would be the most honest solution in my opinion.

If I win a game, when can I expect to receive it?
Giveaway creators are allowed one week to send the gift after their giveaway has ended. Depending on the type of gift and the giveaway creator, you might receive the gift to the email address you have listed on the account page, a key might be added beside the gift you won, or the giveaway creator might have sent you a friend request on Steam to make the exchange. Please remain patient, and do not contact the giveaway creator during this time. If the gift is not received after one week, you can mark the gift as not received, and attempt to contact the giveaway creator on Steam to follow-up.

Also can a winner ask for giveaway to be deleted if the creator hasn't logged in?

No, deleting GA without creator ticket would mean that they lose the giveaway slot as well. Someone with not many sent gifts could get locked from making new GAs that way, and would need to contact support and wait for someone with high enough permissions to un-delete GA to recover the slot. Easier to keep Not Received if needed, and change to Received after creator sends the game.

Personally I would like to give the person some extra time

Just keep it in "Awaiting Feedback", but remember it will prevent you from entering other GAs for the same game. So it's trade off between being nice and being able to win the game you want to have.

So basically what people above me wrote.