Correct spelling for the English word "endest" is [ˈɛndəst], [ˈɛndəst], [ˈɛ_n_d_ə_s_t] (IPA phonetic alphabet).
The word "endest" is actually a rare archaic form of the word "end". Its etymology can be traced back to the Old English word "endian", which means "to bring to an end" or "to finish". In Middle English, it evolved into "enden" before taking on the form "endest" in the second-person singular present tense. Over time, this particular form fell out of use and was replaced by the modern "end" that is commonly used today.