Endangered languages are considered to be dying out in a meaningful way, by losing their speakers.
All languages are equally "endangered", if you mean dying in the sense that Latin did, where it was and still is one of the most successful languages of all time.
Latin is not spoken natively anymore except for really rare special circumstances (much like Esperanto and Klingon have occasionally been taught/picked up by young children).
All languages are equally "endangered", if you mean dying in the sense that Latin did, where it was and still is one of the most successful languages of all time.