Hello! How can I implement a controlled animation of the disappearance of an object in Krita without difficulties? Before that, I had to use a erase in every key frame

It depends on what kind of 'simple disappearance' you want to have.
It also depends on the nature of the artwork and how it's distributed between the different animated layers.
This kind of discussion would need screenshots and other images.

I suggest that you go to https://krita-artists.org/ (sign up and sign in needed) and create a New Topic for your question.
That forum is well suited to posting images as part of a discussion and images will be needed for this.