I got 2, maybe so far, but i doubt there is more.

The Fatal Error: Make the menu freak out, by ending the match via killing the enemy with "add text here" on the screen.

Achievement Name (or something like that): Idk how exactly to get it but you can get by taking damage and randomly getting turned into the 1's and 0's like in the matrix or something, idk.

I'm not sure, but I think I got The Fatal Error by using Down B on my last stock, and then holding up so that MissingNo. self-destructs.

(By the way, you can determine the effect of Down B by holding up, down, forward or back! Up is self-destruct which takes up a stock, down is burning and freezing the foe at the same time, holding towards the opponent applies the healing rocks from Abyss mode, and holding back from the opponent just seems to glitch palettes/turn on negative percent sometimes. I've seen other effects too, like MissingNo. summoning an arrow-looking thing and throwing the opponent backwards, but I don't know if there's a way to get that to happen consistently. Otherwise, if you don't hold a direction, it's random.)

Here's an odd one. Syntax Error, not sure how i got there, but after messing around in Practice mode when the screen was odd, I backed out and it was el glitchy game again.

When I went to Milestone afterwards, I gained the achievement. I've done nothing but go to Practice Mode, get the glitchy screen, backed out, then went to Milestone.

Maybe I forgot what I did before, but it is something.

I just checked this, it works! I think I've figured it out fully now.
You need to battle with MissingNo. in anything until the screen and UI is glitched. Once you've done that, head back out to the CSS. Without unselecting MissingNo. and unloading it (don't hold B or anything to back out, since that'll unselect MissingNo.), you need to go out of the CSS to the main menu of the game, and then go into Milestones.

引用自 ØneofaK1nd：

Here's an odd one. Syntax Error, not sure how i got there, but after messing around in Practice mode when the screen was odd, I backed out and it was el glitchy game again.

When I went to Milestone afterwards, I gained the achievement. I've done nothing but go to Practice Mode, get the glitchy screen, backed out, then went to Milestone.

Maybe I forgot what I did before, but it is something.

Ok, so the way to get the Fatal Error achivement is to DSpecial so MissingNo makes the opponent negative then kill with FAir.

there's a spot in the character selection portrait (bottom left) that can be clicked. When the match starts and it is active, the GUI elements will already be glitched before anything happens. Does anyone know what it does?

引用自 AsierX06：

there's a spot in the character selection portrait (bottom left) that can be clicked. When the match starts and it is active, the GUI elements will already be glitched before anything happens. Does anyone know what it does?

that's just a toggle that got added in an update that turns off the more intense visual effects and prevents missingno from screwing with stuff outside of matches.

i had a achivement called: ACHIVIMENT0101010101010101010101010

apparently you can unlock the binary skin/achievement0101 by sheer luck!! down special (up input) can sometimes have you respawn as a different skin after self destructing, with this skin being one of the rare ones to come across

i found this while trying to get the default skin on yellow missingno, so im unsure if getting the binary skin is exclusive to yellow missingno's down special table (becareful!! closing the game locks the costume again)

fun fact: there's some weird golden things that appear in missingno everytime you get a badge

how do I see my achievements

引用自 viscidFelidae：

引用自 AsierX06：

there's a spot in the character selection portrait (bottom left) that can be clicked. When the match starts and it is active, the GUI elements will already be glitched before anything happens. Does anyone know what it does?

that's just a toggle that got added in an update that turns off the more intense visual effects and prevents missingno from screwing with stuff outside of matches.

what about the milestone? it doesn't remove the weird stuff

What are achievements for?

引用自 millennial on cell phone：

I'm not sure, but I think I got The Fatal Error by using Down B on my last stock, and then holding up so that MissingNo. sus self-destructs.

(By the way, you can determine the effect of Down B by holding up, down, forward or back! Up is self-destruct which takes up a stock, down is burning and freezing the foe at the same time, holding towards the opponent applies the healing rocks from Abyss mode, and holding back from the opponent just seems to glitch palettes/turn on negative percent sometimes. I've seen other effects too, like MissingNo. summoning an arrow-looking thing and throwing the opponent backwards, but I don't know if there's a way to get that to happen consistently. Otherwise, if you don't hold a direction, it's random.)

idk if its an update but Down b + up doesnt take a stock

I got an one called @ACHIEVEMENT_NAME