てしまう・ちゃう・じゃう - Grammar Discussion

Hello @Fuga ! Thank you for your explanation as it definitely cleared things up.

I did not realize that 終わる was intransitive… I now see the reason why the causative was used. If I may ask, would it be different if I were to use 終える instead?
ゲームを始める前に宿題を終えてしまおう。
This one seems to make sense grammatically, but I wonder if it really is correct.

Glad it cleared things up!

終える has the same meaning as 終わらせる. However 終える has the added nuance of something ‘ending/finishing naturally’/‘letting something come to an end on its own without putting in effort’, while 終わらせる by itself has a stronger nuance of ‘working/putting effort into finishing something’. Because of this added nuance in 終える, it sounds very unnatural when paired with てしまおう(Let’s completely finish).