Fulminate is a verb that means to be severely against something and extremely vocal about one’s opinion. It can also be used to describe something exploding suddenly or be instantly violent. In medical terminology it is used as an adjective in the form fulminating to describe a disease that came on quick and strong.
The noun form is fulmination.
In science it is also the name of a compound using fulminic acid. Incidentally these compounds usually are highly explosive.
Culminate is a verb that means to arrive at or be the end or the outcome of an event or action. In can also mean for something to reach its highest point, like a star or planet. When used with an object it means to bring it to the end or to its peak.
The noun form is culmination.
The culmination of something very well could be a fulmination, but not always.
Examples
But for every fan won over by Mumford & Sons’ rollicking, blood-on-the-banjo approach, it seemed, a naysayer would fulminate at the band’s neo-rusticism – a pose imbued with certain class connotations in the UK. [The Guardian]
The paranoia about Jade Helm, which started on websites like Alex Jones’s InfoWars, had started with familiar fulmination about a mass seizure of firearms or a cover-up for American “death squads.” [Bloomberg]
The founders of these companies use their seed capital to efficiently orchestrate a process-oriented set of experiments that culminate in evidence of product-market fit. [Tech Crunch]
He also explained the circumstances which culminated in his interplanetary fulmination. [Gothamist]
“Fulminant” is probably more common in medical records (I read a lot of them at work) than “fulminating”. I think the distinction may be immediacy–fulminant liver failure came on strong a while ago, and fulminating liver failure is coming on strong RIGHT NOW.