When the two witnesses have finished their testimony, the beast that comes up from the Abyss will wage war with them, and will overpower and kill them.
KJV
And when they shall have finished their testimony, the beast that ascendeth out of the bottomless pit shall make war against them, and shall overcome them, and kill them.
ASV
And when they shall have finished their testimony, the beast that cometh up out of the abyss shall make war with them, and overcome them, and kill them.