Stuff Tekken Borrowed From Other Video Games
No doubt video game companies have the habit of copying each other which in this case, no copyright infringement was being done. Here's a few stuff I thought can be raised up:
Tekken took some ideas from Virtua Fighter. From Nina Williams being an obvious Sarah clone, you could consider the idea of a realistic martial arts fighting game with an unrealistic story is also Virtua Fighter's concept. Later concepts from Virtua Fighter might add to the additiion of Raven as a Kage Maru type character, Leo in Tekken 6 is somewhat inspired by Lion in Virtua Fighter and Wang Jinrei is similar to Shun Di.
Taking concepts from Street Fighter. Tekken 2 added the character Ganryu who looks like E. Honda then Taka-Arashi was made for Virtua Fighter 3. Kazuya having an evil self is similar to Evil Ryu but with a darker twist. Mishima Zaibatsu is the Shadaloo of Tekken being involved in unethical science wanting to dominate the world. In Tekken 5 Dark Resurrection both Asuka and Lili are similar to Sakura and Karin. Asuka aside from being a Jun Kazama type character, she like Sakura is your school girl type character.
Heihachi Mishima seems to be a mixture of several characters. He looks like Dr. Wily in Megaman. Like Shang Tsung in Mortal Kombat he is a conniving old man who seeks to become immortal (strangely Cary Hiroyuki-Tagawa played as him in that awful Tekken film). Like General Bison (Vega in Japan) he owns a corporation of evil while holding a tournament for money. Like Dr. Wily he is also a comical villain at times but not to be underestimated. In Tekken Tag Tournament 2, he had his youth restored though it is not canon at all.
Supernatural and monster type final bosses. I don't know which game I can attribute it to but I might want to think of Mortal Kombat for one. Later like Mortal Kombat, Tekken featured unplayable final bosses in Jinpachi and Azazel due to their insane strength. Later Jinpachi was powered down for Tekken Tag Tournament 2. Tekken Tag Tournament 2 featured a death animation for Unknown that is after defeating her and she lies down, you see a full CGI video of her defeat.