The qualification for being a Christian is that you believe in Christ. That is literally it.
No, the qualification for being a Christian is that you follow Christ. The Biblical writer James actually addresses this very thing ad absurdum by showing that, if the qualification is only to believe in Jesus, even the demons are Christians. Repentance is the first act of selecting into the group of “Christian.”
You can be the worst person ever and be a Christian.
No, you can have been the worst person ever and be a Christian. Repentance begins the journey and remains a constant throughout; as Martin Luther said in the first of his 95 Theses, “When our Lord and Master Jesus Christ said, ‘Repent,’ he willed the entire life of believers to be one of repentance.”
In fact, most Christians believe that everyone is a sinner, so being horrible is basically expected and accepted.
I’m so sorry that you’ve been given such a twisted view of this, though I totally understand why (I’ve seen this argument being made, particularly about Trump in 2016). Being horrible is explicitly not expected or accepted; Jesus himself causes people who claim faith but do awful things “vipers” and weaves a whip to use on them to prove he’s serious. The biblical writer Paul asks rhetorically, “shall I continue sinning so that grace may abound? God forbid!” And theologian after theologian for 2,000 years has said the same. If you’re gleefully continuing in being horrible, you’re proving that you aren’t a Christian; and Christians since the first century have affirmed that definition of the faith.
Finally… someone who knows what the fuck they’re talking about around here. It’s so refreshing to see someone who is actually familiar with the texts in question and the historicity of these claims.
It’s people like you that keep me wading through all this sewage and garbage.