The only qualifying factor of heaven is acceptance of Christ Jesus. But Jesus tells us to look and judge the fruit of the tree (and thus, the life of an individual). If a tree is good, it will produce good fruit. If it is bad, the fruit is bad.
However, you have to understand that the more we sin, the harder our hearts become. We know when we do something wrong. There are moments of guilt or shame that follow us doing something wrong, but after awhile, we don't want to live that. So we either repent and confess, or we harden our heart to it.
I would suspect someone like Hi7ler had a hard of stone. And it's a
hardened heart which prevents us from seeing the goodness of God in order to accept Christ. But again, God has promised to give a new heart to those who look to Him.
"And I will give you a new heart, and new spirit I will put within you. And I will remove the heart of stone from your flesh and give you a heart of flesh." - Ezekiel 36:26
I do not know what happened to Hi7ler. If he accepted Christ, then yes, he would be in Heaven.