Is it correct to say, it is I who has done this or it is I who have done this.
This is a question that, in some form or other, has been asked hundreds of times in this and other forums. Some people have quite strong views. Whichever form you choose, some people will consider it to be incorrect.
The safest answer is to avoid this type of construction and simply say, "I have done it".
I am the one who has done it.