Certainly all liars will end up in the lake of fire. But there again, lies can be repented of. Self-murder cannot.
If man's last act on the earth is evil, can it truly be said that that man was a good tree as Jesus spoke of? No good tree can bear evil fruit.
Again, how can one deny oneself and still be so selfish that one kills onesef? And if one murders oneself and is allowed entrance into the Kingdom, escaping the lake of fire, then Revelation 21:8 is clearly a lie.
Revelation 21:8 But the fearful, and unbelieving, and the abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death.
It is undeniably in the Word that all murderers (and yes, all liars as well) shall be cast into the lake of fire.
Suicide is murdering oneself, there is no getting around that.
So, either Revelation 21:8 is truth and no murderer will inherit the Kingdom, or it is a lie and it is ok for anyone to play the part of God and take life and be guaranteed acceptance into the Kingdom.
Maybe John was lying when he also wrote that 'no murderer hath eternal life abiding in him' (1 John 3:15). That verse alone would show that the one who commits suicide was never saved; after all, suicide is murder.