Samurai X, the OVAs to the popular series Rurouni Kenshin. The new title may throw off some viewers. Kenshin's not a samurai but an assassin, and the scar is never refered to as an X, only as "cross-shaped." Maybe a more appropriate name would be "Assassin Cross." Wow, that's cool. But a name change is appropriate. "Samurai" because Kenshin is refered to as a samurai a couple times in the manga, and "X," likely because "X" was a former movie rating designating mature adult content, lets people know that this story is for adults, not the teenagers the series targeted. As well, looking at the cover, in which the "X" nearly covers the word "samurai" is symbolic: this show coverse the end of the Edo period, in which the samurai class came to an end, or was ex-ed out.
Samurai X is violent and about violence. Plenty of films have abundant violence (I don't need to give you any examples, I'm sure), but most of them aren't mature explorations of violence and its consequences. These OVAs show us that violence is messy: you will get bloody, you will get that pretty dunk woman bloody, you will kill people who are fighting for ideals just as you are, the people you kill will leave behind family and friends who will miss them, and you will deal with the psychological pain for the rest of your life. And that's really all I have to say. That's all I can say without spoiling it.
Trust & Betrayal is one of the best things ever animated. It is the Star Wars prequels done right: a nine-year-old orphan (Kenshin) sold into slavery after his parents die is rescued by an expert swordsman (Hiko) who follows a special form of fighting and takes the boy to train him after he sees him do a physically-demanding task. Kenshin then turns his back on his master when a war comes up, trying to save people while killing as many as he can. Hiko is Obi-Wan and Yoda,and what the prequel Jedi should have been: one of a group of knights that basically keep to themselves and help people wherever they find injustice (rather than being a practically militant group who fight in wars). Hiko doeos not want Kenshin to fight a war and align himself with a side: he should deal with injustice on a case-by-case basis, wielding a sword for the world, an idea young Kenshin cannot grasp. We then see the consequences of his brash choice, one that will haunt him the rest of his life.
And the art is some of the best ever put to paper. Not only the art, but the animation. There's a part where Kenshin takes a piece out of a fish with chopsticks; usually any bites taken out will be foreground, while the fish is background, so the two pieces will look different visually. Here, the entire fish looks like the background; he pulls a piece out, and the hole in the fish looks like the background still. Hard to describe, I know, but I was dazzled by the effort put into the smallest of movements.
Now that I've finally got the hang of reading manga, I've read the final volumes to see how the story ends. I thought that the explanation of how Kenshin got his scar was better in the OVA. It didn't seem plausible in the manga, nor was the explanation worthy of one of the most iconic scars in literature/film, whereas the anime changes it to be poignant and tragic.
Reflection finally cements what the whole Rurouni Kenshin story is: a character epic. We begin at "Trust" seeing a young, inexperienced Shinta. Then we see his assassin days, then his wanderings, then his regrets at his end days. Some people, even the creator, don't like it because of the melancholy, downer ending. Well, what did anyone expect? Megumi said at the end of season two that Kenshin's body was not capable of much more abuse, and Hiko states that Kenshin's body build is not strong enough to withstand Mitsurugi style and will deteriorate from using it. Added to that the psychological pressures of his former violent lifestyle, which war veterans will tell you never fully go away, I am not surprised to see what happened to Kenshin. It is sad, but understandable, and actually not as horrible as people think. There are a lot of things to be happy about in the way Kenshin comes to the end of his life. I'll give just one: he sticks to his vow never to kill again. That in itself merits a happy ending.
Do not watch Samurai X until you've seen Rurouni Kenshin. It is easy to follow, as it takes place earlier, but you do not need the explanation of the scars' origin hanging over your head during the more comedic series of the show.