Possibility

I don't think he'll pass

100

odds

The odds are against him passing

200

probably

He probably won't pass.

300

unlikely

It is unlikely that he will pass. 

He is unlikely to pass.

400

likelihood

There is little/ no likelihood of him/his passing. 

500

doubt

I doubt if/whether he will pass. 

I have my doubts as to whether he will pass.

I'm pretty confident of her passing

100

odds

The odds are on her passing.

The odd are that she will pass. 

It is odds-on that she will pass. 

200

probability 

In all probability, she will pass.

The probability of her passing is high. 

300

doubt

I have little (or no) doubt that she'll pass. 

I don't doubt that she'll pass.

400

bound

(I feel) she is bound to pass.

500

prospects

Her prospects of passing are very good.

The prospects of her passing are very good. 

She has good prospects of passing.

I doubt if I'll ever see him again

100

likely

We are not likely to see him again.

200

surprise 

It would be a surprise if we saw him again.

It would come as a surprise if we saw him again.

300

chances

The chances are we won't see him again.

There is little/ not much chance we'll see him again.

There is little/not much chance of us/our seeing him again. 

400

prospects

There are few prospects of our seeing him again.

The prospects of our/us seeing him again are slim.

500

well

We may (very) well never see him again. 

No one can be at all sure of the outcome

100

far

We are far from sure of the outcome.

The outcome is far from certain. 

200

uncertainty 

There is (general) uncertainty about the outcome. 

300

unpredictable

The outcome is unpredictable. 

400

certainty 

There is/can be no certainty about the outcome. 

The outcome is far from being a certainty. 

500

laps of the gods

The outcome is in the lap of gods.