All 10 Uses of

contrary

in

Le Morte D'Arthur, Volume II

When Sir Dinas understood that King Mark would go upon the miscreants, then Sir Dinas in all the haste put down all the people; and when the people were departed every man to his home, then King Mark espied where was Sir Tristram with La Beale Isoud; and there by treason King Mark let take him and put him in prison, contrary to his promise that he made unto Sir Percivale.†
Book 10

contrary to = in opposition to

How the second day Palomides forsook Sir Tristram, and went to the contrary part against him.†
Book 10

He might well say it, said the hermit, for when ye were first made knight ye should have taken you to knightly deeds and virtuous living, and ye have done the contrary, for ye have lived mischievously many winters; and Sir Galahad is a maid and sinned never, and that is the cause he shall enchieve where he goeth that ye nor none such shall not attain, nor none in your fellowship, for ye have used the most untruest life that ever I heard knight live.†
Book 13

Also the dry tree and the white lily: the dry tree betokeneth thy brother Lionel, which is dry without virtue, and therefore many men ought to call him the rotten tree, and the worm-eaten tree, for he is a murderer and doth contrary to the order of knighthood.†
Book 16 *

contrary to = in opposition to

Slay him will I, said he, whoso say the contrary, for he hath done so much against me that he hath well deserved it.†
Book 16 *

So in this meanwhile came in Sir Mador de la Porte, and took his oath afore the king, that the queen did this treason until his cousin Sir Patrise, and unto his oath he would prove it with his body, hand for hand, who that would say the contrary.†
Book 18

Come down, traitor knight, said he, and make it good the contrary with thy hands, for it mishapped me the last battle to be hurt of thy hands; therefore wit thou well I am come this day to make amends, for I ween this day to lay thee as low as thou laidest me.†
Book 20

Madam, said Palomides, ye may say whatso ye will, I may not contrary you, but by my knighthood I knew not Sir Tristram.†
Book 10 *

Now, said the lady, sithen ye be set among the knights of heavenly adventures, if adventure fell thee contrary at that tournament have thou no marvel, for that tournament yesterday was but a tokening of Our Lord.†
Book 15

Definitions:

(1) (contrary as in: a contrary idea)
different (perhaps opposite or mutually exclusive)

In formal logic, contrary propositions or contrary arguments describe two things that cannot both be true. They might be described as mutually exclusive. For example, a pet cannot be both a cat and a dog. It doesn't need to be either, but if it is one, it cannot be the other. So the statement that a pet is a cat and the statement that the same pet is a dog, are contrary statements.
(2) (contrary as in: a contrary personality)
disagreeable -- typically in reference to someone's personality
(3) (contrary to as in: contrary to)
in opposition to

You could also think of this as meaning, despite, or in spite of, or in conflict with; but since a common meaning of contrary is opposite, you many find it easiest to think of contrary to as in opposition to.
(4) (on the contrary as in: on the contrary)
an expression used to intensify denial of an idea

More rarely, on the contrary is used to oppose an idea contained in what was just said rather than to oppose what was literally said. Here is an example: "I will not pay you for the work. On the contrary, I may sue you for damages." Suing for damages does not oppose not paying, but it does oppose the idea of paying.
(5) (to the contrary as in: to the contrary)
with an opposite or different effect; or something with an opposite or different effect
(6) (meaning too rare to warrant focus)