Initial translation said something along the lines of Allen 'killing that person' though later it was translated as 'one you love' which probably is more accurate.

Kanda said, "I can't die until I find that person."

Granted, I'm not saying that's my prediction, but more me really not being surprised. I'd be disappointed if it was Lenalee because that'd be so obvious, but also I'd be heartbroken if Allen and Kanda had to really duke it out. Could also have their fighting between them be a sort of prelude to it.