Segal is expert in Aikido, but that is at the very bottom of the list of supposed deadly martial arts. He adds stuff to it and soups it up with movie techniques to make it look deadly, but it's not.
There's a famous anecdote in which Segal challenged Gene Lebell, old school judo expert, and MMA fighter before it was MMA. LeBell choked him out easily. Lebell was an all around tough guy--could have taken out most modern MMA dudes easily. Segal is a paper tiger, a movie actor who thinks he's tough, IMO.
Here's Chuck Norris (a full contact world champion) calling Seagal a "wannabe":