1. Coming judgement was a big part of Jesus' teaching.
2. 'This generation' is repeatedly mentioned and we are told judgement is coming on them.
3. The judgement Jesus talks about involves sorting people out into two groups, rewarding one group and punishing the other group.
4. If life for the righteous is eternal, then so is punishment for the wicked. (Matt 25:46)
5. God seems to be punishing people because he is angry with them.
6. God's judgement is well deserved. The people Jesus was speaking to/about had done bad things.
7. Fire is often used as an image of what judgement is like. Not so much, I think, to purify the evil as to dispose of it.
8. Judgement can be escaped.