Ruddy is a British English expression, so an American like me may be wrong, but I think "ruddy" is just an intensifier to make the expression more strong. "Ruddy" may be a variation of "bloody," which the English often use as an intensifier.

There are lots of examples like this. Sometimes you might feel like swearing and the actual swear words would be "bloody hell". If you don't want to offend people or if there are children around you might modify the words in a humorous way and say something like "ruddy hell" or "blinking heck" or similar. The words don't actually mean anything - they just sound a bit like the actual swear words. "Flipping heck"' is another version which would be said instead of " Fu**ing hell"

John is correct, Ruddy is used as a euphemism for "bloody" sometimes bloody can come across too strong a word especially for a children who might watch the movie so ruddy is a less intense way to say bloody. the term for this is called a "minced oath" which replaces or misspells profane or offensive terms to reduce the offensive characteristics of the original term other examples of this can be "Gosh" instead of "god" or "Darn" instead of "damn"

Ruddy hell! I haven't heard anyone say "ruddy hell!" for ages. Used to be very popular in my youth. Fallen out of fashion a bit, I think.

John is correct, Ruddy is used as a euphemism for "bloody" sometimes bloody can come across too strong a word especially for a children who might watch the movie so ruddy is a less intense way to say bloody. the term for this is called a "minced oath" which replaces or misspells profane or offensive terms to reduce the offensive characteristics of the original term other examples of this can be "Gosh" instead of "god" or "Darn" instead of "damn"