Zechariah 12:9
Zechariah 12:99So on that day I will set out to destroy all the nations that come against Jerusalem.
JWs read this as Jehovah's own first-person promise to destroy the nations that come against Jerusalem at Armageddon — fitting their theology of Jehovah as the warrior who defeats his enemies through his organisation.
The verse is load-bearing for the deity-piercing argument because it nails down the speaker's identity one verse before the piercing claim. Verse 9 is unambiguous first-person Jehovah-speech — "I will be certain to annihilate all the nations". Verse 10 continues with the same first-person speaker — "I will pour out... the spirit of favour and supplication, and they will look to the one whom they pierced". The grammar binds the warrior of verse 9 and the pierced one of verse 10 to the same divine speaker. Use this verse to establish that no speaker change has occurred between 9 and 10.