In the original Highlander Ramirez says this to Macleod:

You are safe only on holy ground. None of us will violate that law. It's tradition.

Even Kurgan obeyed it, despite his lust to have the prize:

Holy ground, Highlander! Remember what Ramirez taught you.

Were there immortals who did not abide by this tradition  / law (in the movies or in the TV series) intentionally?

This answer, shows that at least in the extended canon of the books Duncan was apparently tricked into violating it.

In the original Highlander Ramirez says this to MacLeod:

You are safe only on Holy Ground. None of us will violate that law. It's tradition.

Even Kurgan obeyed it, despite his lust to have the prize:

Holy ground, Highlander! Remember what Ramirez taught you.

Were there Immortals who did not abide by this tradition/law (in the movies or in the TV series) intentionally?

This answer, shows that at least in the extended canon of the books Duncan was apparently tricked into violating it.

In the original Highlander Ramirez says this to Macleod:

You are safe only on holy ground. None of us will violate that law. It's tradition.

Even Kurgan obeyed it, despite his lust to have the prize:

Holy ground, Highlander! Remember what Ramirez taught you.

Were there immortals who did not abide by this tradition / law (in the movies or in the TV series) intentionally?

This answer: https://scifi.stackexchange.com/a/14042/1148, shows that at least in the extended canon of the books Duncan was apparently tricked into violating it.

In the original Highlander Ramirez says this to Macleod:

You are safe only on holy ground. None of us will violate that law. It's tradition.

Even Kurgan obeyed it, despite his lust to have the prize:

Holy ground, Highlander! Remember what Ramirez taught you.

Were there immortals who did not abide by this tradition / law (in the movies or in the TV series) intentionally?

This answer, shows that at least in the extended canon of the books Duncan was apparently tricked into violating it.

In the original Highlander Ramirez says this to Macleod:

You are safe only on holy ground. None of us will violate that law. It's tradition.

Even Kurgan obeyed it, despite his lust to have the prize:

Holy ground, Highlander! Remember what Ramirez taught you.

Were there immortals who did not abide by this tradition / law (in the movies or in the TV series) intentionally?

This answer: http://scifi.stackexchange.com/a/14042/1148, shows that at least in the extended canon of the books Duncan was apparently tricked into violating it.

In the original Highlander Ramirez says this to Macleod:

You are safe only on holy ground. None of us will violate that law. It's tradition.

Even Kurgan obeyed it, despite his lust to have the prize:

Holy ground, Highlander! Remember what Ramirez taught you.

Were there immortals who did not abide by this tradition / law (in the movies or in the TV series) intentionally?

This answer: https://scifi.stackexchange.com/a/14042/1148, shows that at least in the extended canon of the books Duncan was apparently tricked into violating it.