Luke 12:5

I will show you of whom you should be afraid. Be afraid of him who, after killing you, has the power to fling you into the Pit. Yes, I say, be afraid of him.

Matthew 10:28

And do not be afraid of those who kill the body, but are unable to kill the soul; rather be afraid of him who is able to destroy both soul and body in the Pit.

2 Peter 2:4

Remember, God did not spare angels when they sinned, but sent them down to Tartarus, and committed them to caverns of darkness, to be kept under guard for judgment.

Matthew 5:22

I, however, say to you that any one who cherishes anger against his brother shall be liable to answer for it to the Court; and whoever pours contempt upon his brother shall be liable to answer for it to the High Council, while whoever calls down curses upon him shall be liable to answer for it in the fiery Pit.

Matthew 25:41

Then he will say to those on his left 'Go from my presence, accursed, into the 'aeonian fire which has been prepared for the Devil and his angels.'

Matthew 25:46

And these last will go away 'into aeonian punishment,' but the righteous 'into aeonian life.'"

Mark 13:23

But see that you are on your guard! I have told you all this beforehand.

1 Thessalonians 4:6

None of you over-reaching or taking advantage of his Brother in such matters. 'The Lord takes vengeance' upon all who do such things, as we have already warned you and solemnly declared.

Hebrews 10:31

It is a fearful thing to fall into the hands of the Living God.

Revelation 14:7

and he cried in a loud voice-- 'Reverence God, and give him praise (for the hour of his Judgment has come) and worship him who made the heaven and the earth and the sea and all springs of water.'

Revelation 15:4

Who will not reverence and praise thy Name, O Lord? Thou alone art holy! All nations will come and worship before thee, for thy judgments have become manifest.'

Revelation 20:14

Then Death and the Lord of the Place of Death were hurled into the lake of fire. This is the Second Death--the lake of fire;

Treasury of Scripture Knowledge

Summary

But I will forewarn you whom ye shall fear: Fear him, which after he hath killed hath power to cast into hell; yea, I say unto you, Fear him.

Bible References

Forewarn

Mark 13:23
But see that you are on your guard! I have told you all this beforehand.
1 Thessalonians 4:6
None of you over-reaching or taking advantage of his Brother in such matters. 'The Lord takes vengeance' upon all who do such things, as we have already warned you and solemnly declared.

Power

Matthew 10:28
And do not be afraid of those who kill the body, but are unable to kill the soul; rather be afraid of him who is able to destroy both soul and body in the Pit.
Matthew 25:41
Then he will say to those on his left 'Go from my presence, accursed, into the 'aeonian fire which has been prepared for the Devil and his angels.'
2 Peter 2:4
Remember, God did not spare angels when they sinned, but sent them down to Tartarus, and committed them to caverns of darkness, to be kept under guard for judgment.
Revelation 20:14
Then Death and the Lord of the Place of Death were hurled into the lake of fire. This is the Second Death--the lake of fire;