The combat is much too difficult, the numbers you're asking for are astronomical in comparison of the other objectives and tools for them. Bosses attack too quickly for shielding to be of any use against them, especially when that starts a combo because the boss keeps attacking while you are unable to take action, rendering your shield useless. Try adjusting numbers to fit for an achievable goal without just getting lucky.
 "Token Hero"){kind=icon}
 "Edmus"){kind=icon}
 "Elephant Quest"){kind=icon}
 "Doodle Devil"){kind=icon}
 "Epic Combo!"){kind=icon}
 "Loved"){kind=icon}
 "D-Day Defender"){kind=icon}
 "ImmorTall"){kind=icon}