Can you just use 'trop' without the 'grand'? You can say 'de trop' in slightly pretentious uk English to indicate something is too much/over the top. But can 'trop' actually be used on its own in real French?
Just confirmed with a native France speaker and I withdrew my previous statement. n6zs is 100% right. You cannot just say le risque est trop... You must follow it with a word such as "élevé", "grand" etc.