Would a Barbarian/Knight hybrid be too contradictory?

Ehh, not so much. Following a code does not make someone a Knight. Druids have codes but they’re not knights. Just as being a Warrior Monk does not make someone a Paladin.
That being said, I think the class “Barbarian” does carry a lot of baggage. However, some versions of “Barbarian” are more variable. Knight, however, not so much. But that’s another story.

ccs said:

What you're looking for is called a.... Fighter!

Click to expand...

Yep, that about covers it.

And I DM'd 1st ed for years. There is no class so hideously, laughably overpowered as the Cavalier. Hell, the designers of Unearthed Arcana even admitted that they didn't playtest it enough before putting it in the rulebook.