The final boss has huge design issues.

[Ninita]

So huge, in fact, that it almost ruined the game for me, which is a shame because I liked it a lot until then.

1. Wait... You can block?
I used Block when it was introduced at the beginning of the game but, since I couldn't consistently get the timing right, I stopped using it and when I fought the final boss 12 hours later, I didn't even remember that it existed.

2. Where's my menu?
You can't access the menu in the final phase of the game, meaning that you can't change the difficulty or look at the controls.

3. Wait... You can do that in this game?
I had to google for 15 mn before I found a post explaining what you have to do to beat the final phase with the spears. NOTHING else works like that in the game.
https://www.trueachievements.com/a391246/the-bigger-they-are-achievement