HATCHBACK CHALLENGE:
Day 1: Max engine, max transmission, max wheels, rest in fuel -- (Travel ~750 ft)
Day 2: Max fuel, get boost, get weapon, buy as much boost, buy as much weapon. Use boost right before fuel ends. -- (Travel ~ 970 ft)
Day 3: Max boost, buy as much weapon. Use boost right before fuel ends. (Travel ~1100 ft)
Improved from (also very good) Grape's tips.
How I easily got the HARD badge:
Choose Celestial Lightwielder (my titles were Legendary and Devastating).
When lvl up, upgrade (equally) only WILLPOWER and INTELLECT.
Don't need any other magic but HEAL and SANCTIFY.
In battles:
Always use SANCTIFY. if you're still losing HP, use heal.
In floor 10+, use 2 or 3 SANCTIFY (Yes, it's stackable \o/). Heal becomes obsolete.
I Tried many other combinations, but this above was very easy.
I Just got impossible: 2 weeks playing eventualy. Easy, but endurance badge.
ELITE is the hardest. (but not hard)
THUNDERSTORM is easy.
FUEL OF WAR is the easiest (only press 3 the entire game, with rare exceptions).
 "Earn to Die"){kind=icon}
 "Upgrade Complete 2"){kind=icon}
 "Hack Slash Crawl"){kind=icon}
 "The Final Death Wish"){kind=icon}
 "Warlords: Heroes"){kind=icon}
 "Balloon Invasion"){kind=icon}
 "Submachine 3: the Loop"){kind=icon}
 "Pillage the Village"){kind=icon}