In the sentence:
He made _________ demands.
Any other adjective than ridiculous.
I need an adjective meaning 'too much but no impossible.'
"Excessive" proposed by Mick is spot on. But the first word that jumped to my mind is "absurd", i guess i was thinking along the lines of your word "ridiculous".
What you need to ask yourself is what do you want to convey? Do you want to stay neutral or do you want to state your opinion that there's no way that demand would be fulfilled.
Excessive is quite a neutral word here. It describes the demand itself, but not the act of the person making that demand. Both "ridiculous" and "absurd" pronounce the judgement and are much more charged.