Here is a full list of all achievements in RUKIMIN’s Disappointing Adventure!. Spoiler Alert!!!
Oh! White Asparagus!
Above are completed by playing the first section normally.
Above are completed by playing the second section normally.
Die x times, presumably on the same save file.
TITLE SCREEN disappointment!
Click the bomb button in the top left.
GAME SELECT disappointment!
From the Erase option, move the cursor one lower.
Located at the beginning of either section. Eat it.
Clicking on the title screen will spawn another player avatar object. Repeat until sent offscreen. May also work during credits.
You were in Rock!
Use the mouse-controlled block at the end of either section to clip yourself into and out of a wall. There may be another way to do this, or there may be a specific wall – I ran through the entire second section doing this but this is likely unnecessary.
Too easy! Piece of cake!
Start a new save file and input the code immediately. Or play through the full game, if you want.
Right before the minecart section, there is a trap that involves faking out two upward spikes and a reverse fake-out. The image used for the reverse fake-out changes each time the trap is activated; repeat until you meet the macho hero.
Thanks to Gaphodil for his great guide, all credit to his effort. you can also read the original guide from Steam Community. enjoy the game.