What is the worst chess opening/defense?

Are you referring to me by any chance?!?

I like the modern, because it sidesteps the Scotch, Rui Lopez and Italian game, all of which I find highly irritating to play against as black, and which people are well prepared in at all levels.

Also, it can easily transpose into King's Indian type structures, which are very solid and rely on logic and concepts rather than stacks of theory.

I used to play the Caro Kann against e4, but there's so much theory to swallow it's untrue, and there's loads of capacity to go wrong!

What are your prefered defenses against 1. d4?

Haha yes I am, sorry!

And I do remember our game transposing into a KID structure, which was anything but boring.

The OP is clueless.  His title says one thing (Worst opening and/or defense) and his post says something else (Openings he personally hates).

Case in point.  The worst opening amongst all "Normal" openings is probably the Grob (and Borg), but the openings I hate most are the Grunfeld and Dragon.

For the philidor, I usually play c3 and follow up with d4, computer engine agrees with me (depth 10, idk depth 20)

Pretty much the grob, cuz if it's not played well, the whole game is awkward for white.

if responding to e4, f5, f6, and g5 are the worst choices 

Ahh, ok.

Alekhine defence isnt that good as it was used to be

there is not bad opening Kevin Bordi did a draw against Carlsen with the grob attack ! And a lot of GM used modern opening like Pirk defense.

this always gets me

What gets me is these early kingside attacks.  I fended off a particularly brutal opponent a while back. 

Talking to some other chess players, apparently those attacks are particularly popular in the scholastic crowd.

My take on that is it's good for a great bump in ratings, but at some point the player ia going tp hit a hard ratings wall, where all the opponents look at early kingside attacks as inferior, and figure the opponent doesn't understand good chess practices, let alone have decent chess playing.

Creepy Crawly is a terrible opening.

A variation of Bird's Opening (1.f4, e6 2.g4) is particularly bad but with some luck you can have a strong kingside attack.

 fool's mate :0

At a higher level than I play at, for sure. But at around 1700-1800, the Modern transposing into KID type structures has served me well (with a couple of self-destructions thrown in for good measure!). But generally, it's resulted in very solid positions as black. It's certainly far less easy to go wrong than with the Caro Kann or any of the swathes of different Sicilian variations.