The interesting feature in this story is that it portrayed his revenge in a positive light. Justice is a moral absolute, and you really wanted him to get those bad guys. And yes, they were always trying to kill him, so the battles were always technically self-defense, but he really was going after them for "vengeance" (his word), and he really did leave "a trail of dead people behind him everywhere" he went (a line used by a police woman who was following her own agenda in the story).
"Vengeance is mine, says the Lord." Revenge has a tendency to escalate, so God (and the government, as God's minister of justice) rightly reserve it to themselves. Seagal's character did not feel that constraint. He is not alone in that sentiment.
A recent event in my life reminded me that most people -- and certainly this one person -- operate on a "quid pro quo" (payback) rule of justice: he perceived me to "lie" about somebody -- actually he misunderstood me, but at the time, after failing a second time to explain what I was trying to say, I decided his agenda was not receptive and I gave up the attempt, which he took as admission of guilt (so he told me later) -- and so he was justified in slandering me falsely in a place where it could do me harm. On another occasion, he took offense at something I said (I still to this day do not understand what was offensive about it), but when a third person told me and I offered a vague apology -- it's hard to repent of a wrong you don't understand -- he came to my office to perform a little ritual I call "The Prisoner Exchange," where all parties in a conflict confess to equal guilt, then "forgive" each other all the way around.
The Prisoner Exchange is a kind of Christianized version of revenge, but not really Christian. Also quite impractical, since the guilt is not necessarily equal, especially if some of the participants are true Christians, unwilling to play the revenge game. For the Exchange to work, everybody must "confess" to something. It's all about saving face, not righting wrongs. So the "forgiveness" is not real either, and tends to be revoked if there is a repeat occurrence.
In true Christian ethics, if you do something wrong, you make it right, and you don't do it again. If somebody does wrong to you, you tell him [Luke 17:3], and if he repents, you forgive him. And if (God forbid) he does it again, you don't dredge up the previous event. This is an assymmetrical relationship. It puts a stop to revenge. It is also really hard to find among Christians.
For a longer explanation, see my essay As
God Forgave Us.