1). He promised he will return.
John 14:1-4, Luke 17:26-36

2). The Dead are resurrected at Christ's return.
All Believers who have died since Jesus
resurrected will be resurrected, while the
unbelievers at the end of the mellenuim.
(Great White Throne Judgement)
I Tess 4:15-18, Rev 20: 4-6

3). Satan is finally & forever defeated at the return
of Jesus. Rev 19:11-17, Rev 20:7-10
The return of Jesus has to happen so Satan can
be judged.
He will be locked in a prison for a thousand
years during the millennial rule of Jesus Christ,
but at the end of the thousand years his lead
out & he goes and decieves the nations. Then
Jesus puts him in the lake of fire forever & ever.

4). The Dirty of Jesus is proven at his return.
Every eye will see him & every tongue will
confess that Jesus Christ is King of kings Lord of
lords. Rev 1:7, Rev 19:16

5). The return of Jesus establishes the authority of
scriptures. (The Bible)
329 times the return of Jesus is mentioned in
scriptures.