I personally had a lot of trouble filling the heartbreak meter in Act 1 (the game very kindly does not want you to fail this early on), so I've compiled some of the questions I came across that helped me finally get the bad date achievement while courting Megaricus! I'm sure it's probably possible with all the other characters, I just had the most trouble getting the good ending with Megaricus personally, so I figured it was a good starting point.

Additional note: it does not seem the "save" v. "risk it" pop up impacts this at all - it simply allows you to save your game. I actually got this achievement after I had blindly clicked "save."

Let me know if I missed or misrepresented anything! I tried to arrange alphabetically by keyword within each section, but it'll probably be easiest to ctrl + f on the page. Any question marks by responses are ones I could use more confirmed input on!

First date questions:

• Does Gigachu come here often?
  
• Is this Gigachu's first time dating a fungus?
  
• Does Gigachu like the <Location Name>?

Miscellaneous questions:

• What is Gigachu's age / how old is Gigachu? (not sure on question phrasing): Same Age confirmed, other two answers not confirmed
  
• What is Gigachu's favorite color?
  
• What kind of conversationalist is Gigachu?
  
• Does Gigachu dream?: No confirmed, others not
  
• Which does Gigachu follow?: Heart confirmed, Stars confirmed, other one answer not confirmed
  
• What type of music does Gigachu like?: Video Game confirmed, Jazz confirmed, other answer also confirmed
  
• Which does Gigachu prefer for a partner?: Younger confirmed, other two answers not confirmed

• Is Gigachu aquatic?: Yes? (don't pick No)
  
• Megaricus wants to know what first attracted Gigachu to them: can pick any?
  
• Does Gigachu think exes can be friends?: Yes or No (don't pick Maybe)
  
• Has Gigachu been more affected by positive than negative experiences?: Yes? (don't pick Neutral)
  
• What is Gigachu's favorite holiday?: Monkey Buffet Festival or Halloween? (don't pick Kanamara Matsuri)
  
• Is Gigachu into fitness?: Yes?
  
• What qualities would Gigachu wish to pass to future generations?: Sense of Justice (don't pick Humor OR Intelligence)
  
• Does Gigachu enjoy games?: Yes?
  
• What does Gigachu go for?: Cold climate or Clement (don't pick Warm weather)
  
• Is Gigachu multilingual?: No? (don't pick Yes)
  
• Is Gigachu musical? Yes?
  
• Is Gigachu into ornamentation?: No?
  
• What is Gigachu's outlook on life?: Optimistic? (don't pick Pessimistic)
  
• Is Gigachu into piercings?: Yes? (don't pick No)
  
• Which does Gigachu prefer?: Follow a plan or Neither, unsure about third option
  
• What is Gigachu most proud of?: Magic? (don't pick Dancing or Humor)
  
• How does Gigachu relax?: Stargazing? (don't pick Meditation)
  
• To what does Gigachu attribute chu success?: Hard work? (don't pick Luck)

• Does Gigachu like animals?: No
  
• Is Gigachu artistic?: No
  
• Is Gigachu big on bridges?: No
  
• Does Gigachu find it difficult to compromise?: Yes
  
• Is Gigachu complicated?: No? (don't pick Yes)
  
• Is Gigachu a fan of concrete?: Yes
  
• Does Gigachu follow current events?: No
  
• Does Gigachu dance?: No
  
• Which most describes Gigachu?: Troublemaker (don't pick Neutral)
  
• Does Gigachu dig deserts?: Yes
  
• What is Gigachu's diet like?: Fresh (don't pick Local OR Organic)
  
• Is Gigachu moved by domes?: No
  
• Is Gigachu educated?: No
  
• How is Gigachu feeling?: Dangerous
  
• Is Gigachu a fan of forests?: No
  
• Which habitat does Gigachu prefer?: The countryside (don't pick The big city OR The small city)
  
• Which height does Gigachu prefer for a partner?: Shorter
  
• Is Gigachu afraid of heights?: Yes
  
• Who is Gigachu's hero?: Kirby
  
• Is Gigachu a history buff?: No
  
• What are Gigachu's hobbies?: Puzzles
  
• Does Gigachu like literature?: Yes? (don't pick No)
  
• What is the most important reason for marriage?: Propriety
  
• How does Gigachu feel about mountains?: Like
  
• Does Gigachu like metal?: Yes
  
• What is Gigachu's top pet peeve?: Nose Picking
  
• Could Gigachu be with someone who didn't share chu political beliefs?: No
  
• Is Gigachu popular?: No
  
• What is Gigachu's opinion on precipitation?: Dislike
  
• Does Gigachu like rock?: Yes
  
• Is Gigachu scientific?: No
  
• How is Gigachu at keeping secrets?: Good? (don't pick Bad)
  
• Is Gigachu ready to settle down in one place?: Yes
  
• Does size matter?: Yes
  
• Is Gigachu theatrical?: Yes
  
• Is Gigachu vegan?: Yes
  
• What's Gigachu's take on walls?: Dislike
  
• Which is Gigachu?: Morning monster (don't pick Neutral)
  
• How does Gigachu feel about wood?: Dislike

First date:

• Does Gigachu kiss on the first date?: No

Miscellaneous:

• Megaricus wants to know what most attracts Gigachu to them: Sense of Justice