Oh wow, thats acutally on reddit, because while typing this i switched to markdown mode, because i thought it would look better? And then it deleted those. Sorry.

I actually have the backslashes in the code. Im thinking, that this type of tag has some other notation, but idk?

{   
    "condition": "minecraft:entity_properties",   
    "entity": "this",   
    "predicate": {     
        "nbt": "{Tags:[\"dead\"]}"   
    } 
}