直到尽头 As a stucky fan, I prefer to translate it to“直到世界尽头”, for Steve Rogers once said a sentence like that:"I'm with you till the end of the line." Hope that it would help.

to the end of the line. the action should stop at the end of the line. for example: (let your draw something) you draw it till the end of the line then stop drawing. in Mandarin, To the end of the line = 直到线的终点。 i don't see the sentence so the translate just i suppose you met the matter.

直到这句话的末尾 直到文章的最后 直到这条线的终点。 It's hard to give an accurate translation since the meaning of "line" is open without a particular context.

Maybe the sentence meaas "到头了“。Hope to helps.

it depends on language environment,or the mandarin using in the project