In order of scumbagginess... you might be a D-bag if you...
Freeze glitch or DC glitch your way to wins. This has yet to happen to me in M25 - so EA might have finally fixed it. But if this was your way of getting wins in the past, you are still deserving of the #1 ranking.
Flip your play more than a few times per game. In fact... your level of dooshbagedness is directly proportional to the number of times you flip your play. I wish EA would implement some sort of fatigue penalty to counter these idiots, who are merely trying to exploit the bad coding in the game... or worse... they just do it because they watch the "pro players" constantly flip. This isn't the MCS bruh.
Onside kick at inappropriate times during the game (everyone knows when you should onside kick). The fact that the game doesn't let the receiving team call a time out or audible to onside coverage means you're exploiting the coding. I used to get caught by this but I've now trained myself to always wait for my opponent to make the call first.
Message anyone after a game with anything other than "gg" - and even that's pushing it in most cases.
Showboat in general - but especially after a play by the CPU that required no skill on your part.
Call more than 1-2 RPO bubbles per game. I hate these plays so much that I keep a list of every formation in the game with a slot bubble... and when I see any of those, I just give up my Nickel CB and put him on a Vert Hook with Hooks set to 0 yards. If you pass commit, it's a guaranteed pick 6. There's no greater feeling in the game than taking one of these to the house against these dudes.
Run a "Goal Line Offense" for all or most of the game. There's an added scum bonus for guys that do this and chew clock the entire game. We can't mention names here but there are a handful of guys on old gen who play this way and it's literally the most frustrating experience to go against them. I wish I could actually talk to these dudes and see how playing this way can be any fun for them? It's just a scummy way to play because you're again exploiting bad coding in the game.
I realize much of the above is specific to the old gen version of the game. But even given these things, I'd still rather play that, than the dumpster fire of a game that we have on current gen.
Feel free to add to this thread. The D-bags need to hear about it.