I'm not sure where you came up with the idea that there are all these repentant serial murderers in heaven. There are a couple of places where murderers are talked about and it's never in the context of wait until you meet them in heaven.
Rev 21:8 NET.
(8) But to the cowards, unbelievers, detestable persons, murderers, the sexually immoral, and those who practice magic spells, idol worshipers, and all those who lie, their place will be in the lake that burns with fire and sulfur. That is the second death."
Gal 5:19-21 NET.
(19) Now the works of the flesh are obvious: sexual immorality, impurity, depravity,
(20) idolatry, sorcery, hostilities, strife, jealousy, outbursts of anger, selfish rivalries, dissensions, factions,
(21) envying, murder, drunkenness, carousing, and similar things. I am warning you, as I had warned you before: Those who practice such things will not inherit the kingdom of God!
Matter of fact, to a Christian, hatred is murder.
1Jo 3:15 NET.
(15) Everyone who hates his fellow Christian is a murderer, and you know that no murderer has eternal life residing in him.
By now you are probably saying to yourself, that you know Christians that surely hate other Christians so how can that be?
Mat 7:21-23 NET.
(21) "Not everyone who says to me, 'Lord, Lord,' will enter into the kingdom of heaven only the one who does the will of my Father in heaven.
(22) On that day, many will say to me, 'Lord, Lord, didn't we prophesy in your name, and in your name cast out demons and do many powerful deeds?'
(23) Then I will declare to them, 'I never knew you. Go away from me, you lawbreakers!'
You really can't judge Christianity by the people you see. You must judge it by Jesus. Even true Christians sin. But true believers do receive the Holy Spirit and they are indeed filled with God's love.
Marv