Just the ones who are being changed in a negative way
You could sell any other Champions you want who you could normally sell (4-Star and below), but you will only get the resources back that were used to upgrade Cull Obsidian and Namor if you sell those Champion during the specified window of time. And the 5 and 6-Star versions of Cull and Namor can only be sold during that window. For any other Champions, only the 4-Star and below versions will be able to be sold, and selling them will only give the resources that would normally be received.You can find the full details on who can be sold and for what by checking out the announcement post here.
You could sell any other Champions you want who you could normally sell (4-Star and below), but you will only get the resources back that were used to upgrade Cull Obsidian and Namor if you sell those Champion during the specified window of time. And the 5 and 6-Star versions of Cull and Namor can only be sold during that window. For any other Champions, only the 4-Star and below versions will be able to be sold, and selling them will only give the resources that would normally be received.You can find the full details on who can be sold and for what by checking out the announcement post here. Sorry to ask might be a stupid question moment: Can you sell 4* namor/cull and below and get resources back?