1. I think him to be a genius.

2. I think him a genius.

3. I think him to be unkind.

4. I think him unkind.

5. He is thought to be a genius.

6. He is thought a genius.

7. He is thought to be unkind.

8. He is thought unkind.

Which numbers are correct ?

And any reason you didn't choose the other numbers?

And what are the differences in meaning?

fire1Which numbers are correct ?

Opinions will vary. These turns of phrase are so old that nobody today has a very good feel for which are right and which are wrong. I don't believe I've ever heard anyone use I think him ... in my entire life, though I've seen it in writing. He is thought to be ... is used often enough, however.

Just on the basis of what I've seen in writing, I'd say that all except 6 and 8 are technically correct even though they're hardly ever used.

You might find this post informative.

difference between "consider" and "consider to"