It’s true that that's not overly positive either, but it’s likely that Xaldin is far more restrained than most people seem to consider him. He hides his thoughts from the world, keeping them to himself with a strict discipline, similar to that of Saïx. Along the same line of thought, consider how much work it would take to control six lances so finely all at the same time. Wouldn't that itself require a great deal of concentration? And so Xaldin, becomes an incredibly deep character, where nothing outside of his discipline and intelligence are recognized for sure.
To some, Xaldin seems to be a sad character, with a deep pain kept inside, where no one can see it. The scars from things he has done, the ways he learned things, and even the things that were done to him that he didn’t deserve are all locked away in the dark, hidden behind a wall of perpetual loneliness and distrust. And those are, in turn, veiled by his immense discipline. This control allows him to do things such as the actions shown in the game. Yes, Xaldin grinned as he abducted Belle, but she was simply part of his plan, a continuation of how he was rousing the Beast’s ire. After what was likely a very cold and unforgiving past, perhaps that malicious grin of his is the only way he can express himself to those he cannot trust.
Despite his immense strength and discipline, the Lancer also seems as though he has his moments of weakness, often when no one else is there to witness them. He quite possibly goes out during the night and gazes at the moon, thinking, remembering, and comparing. He might occasionally have nightmares, visions of a traumatic past that he’d rather forget. The distrust that he would have developed keeps him from telling even those he manages to grow close to the whole truth and cause him to keep the terrible pain to himself, not out of concern for the others but to keep them from leaving. Behind his brilliance, hidden beneath so many protective layers, is likely really just a simple child, trying to find someone that will stay with him, no matter his flaws but with the misbelief that he must hide the darkest parts of himself and what he’s been through.
Regretfully, this is merely an overview of a more thoughtful way of looking at Xaldin’s character, of attempting to see the man hidden behind the fierce appearance.
Xaldin first appears in Hallow Bastion (Kingdom Hearts II), tempting Beast to use the darkness. Later, he fights Sora after a failed attempt to kidnap Belle and Beasts' rose. The key to defeating him is the use of the Learn reaction command, which does massive damage. Many players found this boss fight difficult because of the few chances to block his many attacks.