1
How dare you to say these things about her?
How dare you say these things about her?
In questions beginning with How dare…?, use the infinitive without to: ‘How dare you speak to me like that?’
2
I dare to say that he is not very intelligent.
I daresay that he is not very intelligent.
I dare say that he is not very intelligent.
I dare say and I daresay are fixed expressions meaning ‘I think something is probably true’: ‘I daresay he’ll call you soon.’
I dare to say has a different meaning: ‘I am brave enough to say something.’