When Marduk went to an abandoned fight arena, during his Tekken 4 ending, Slater appeared and introduced himself, offering a handshake to which Marduk ignored. Slater changed his complimentary attitude and cockily challenged Marduk to a fight, saying that it will be the best unofficial bout ever and alluding to Marduk's expulsion in the wake of a scandal.
Marduk ignored him again and tried to leave, but was stopped in his tracks by Slater, who smugly accused him of running away and being scared of seeing "legendary fighter KO'ed in the headlines." Jeff was eventually taken down by a single headbutt by Marduk, who proceeded to step on him as he left the arena after threatening him not to get up.
Going by first impressions, Jeff seems to be a cocky and self-centered man with a huge ego.
- Craig Marduk - Slater was supposedly a fan of Craig. Despite this, he is incredibly disrespectful towards him as he is seen taunting, mocking and challenging him to a fight. Only to be almost immediately knocked out by one of Marduk's headbutts.
Jeff fights using Vale Tudo. Vale Tudo is a fighting style that generally can be a mixture of any kind of fighting styles, ranging from wrestling, to Judo, to Sambo, to Muay Thai.
Slater is never seen in a fight so his form of Vale Tudo is unknown. However, since being the current Vale Tudo champion, he is more than likely a skillful and formidable practictioner in the form that he does use.