1. D4 c6 as black

I’ve been having good luck with c6 against 1d4 lately. Does anyone else do this? I like playing the Slav and caro kann and this seems to result in players playing lines I know well as black on a regular basis.

It’s kind of like a reti or pirc where I don’t go for the center and force my opponent to think of what I might do next lol. It might just be psychological but c6 seems to be solid.

what the worst possible outcome out of the opening playing 1. D4 c6 vs black?

What’s the advantage of 1…c6 over 1…d5? And to answer your question the worst outcome is 2.e4! taking central space.

The only valid reason why someone would choose to play c6 as a response to d4 would be if they wanted to offer to go into a Caro Kan. If white likes playing against the Caro (which is unlikely, nobody likes playing against the Caro), he can accept but also has to deal with the fact of his opponent inviting the Caro. A similar choice occurs if the opponent plays e6 before Nf6 on his way to a Nimzo, offering the French instead.

The most absolutist classical theory would claim e4 is the best response since pawns at d4 and e4 are better than at d4 and c4, which is probably why the vast majority play d5/Nf6 as their first move with black (preventing e4). It's the same sort of theory that would consider the English inferior. As has been known for hundreds of years d4 and c4 can be just as good, while the Caro and French can be troublesome.

To me that’s the best outcome because we’re playing the botvinnik carls which I know very well!

Most people that start with 1.d4 won’t switch into an e4 opening, so although you’ll get some Caros it’ll be rare. Drawback of …c6 immediately vs 1.d4 is it’s a bit limiting against sidelines where’d you’d have been better served playing …c5 in one go. (For example I think the London System becomes a bit more decent against this move order)

That said, there’s nothing massively wrong with it but not a move order I’d personally adopt even if I played the Caro.

Like others have said, there's nothing really objectively wrong with 1...c6 against 1.d4. But it's definitely a bit restrictive.

I try to play a different flavor of game against d4 than I do against e4 - for the sake of variety. So I personally wouldn't want all my defenses to feel similar. I'd rather have them feel different and varied, if possible, from game to game.

More unique structures to learn and explore = more fun.

I'd say that the worst possible outcome is 2.Bf4. I was looking at different ways to play against the London while looking through "The Agile London System" and responding in the style of a Slav Defense just seemed too shaky for me.

I mean if you decline a gambit there are higher chances like Englund —> Center Game and Scandinavian —> Blackmar

I almost always play Qb6 after Bf4 and have pretty good results agains the london. I hate the games that result from it, but I score well enough. London players typically don't like being pressured while they are mindlessly setting up their pieces.