If you are struggling with those two achievements, there is a way around it if you've completed all the other achievements (ie: coins & npc killing ones). Just go to:

C:\Users\Username\Documents\SavedGames\DLC\DLCQuest Data\AllPlayers

Main game = dlcquest_savegame.xml
lfod_savegame.xml = freemium and die

Make a copy of both (just in case). Open the file in notepad. Scroll to the bottom.

Where is says your tick count (these numbers will vary): <ElapsedTicks>1234567890</ElapsedTicks> Just erase the numbers and put 0.

So it's <ElapsedTicks>0</ElapsedTicks>. Save and start up your game. Now go beat the final boss, wait until credits roll, then you should have the achievement.

Sure this isn't the legit way to get those two achievements...but if you just want the achievements and 100% completion, it's better than struggling for hours on end...and no you won't be able to upload your score at end so it's doesn't mess with the rankings of people who really did it the way it was intended to.

Credit: Mhill2029 for suggesting it in another post.