He's a tricky one, isn't he... Hope you managed to defeat him eventually!
If you are still blocked, the guide to get all endings can be found here: Walkthrough guide in the Devlog section of this page
Awww thank you so much! ^^ We got a new mini update out earlier this month with voice acting, new SFX (you can play music with the menu buttons now XD) and translations. We've also been working on the longer extended version with more endings and achievements, hopefully we'll be able to get it out soon!