It's a title slide, there isn't really space for actual clever word play. You can use some other single word for emphasis, you can make "important" even bigger,

It's a title slide, there isn't really space for actual clever word play. You can use some other single word for emphasis, you can make "important" even bigger, or I guess use some exclamation points, but those are kind of invisible. Or you can do with out any emphasis and just go with a affectless title slide. Whatever you go with, using 'fucking' only looks like a grammatical trick (or more of a trick than using 'extremely' say) if you do still cringe at the word or are still a little opposed to it.