According to various Canadian academic websites, I have found that "with distinction" is all that is needed for Canada, and while terms in Canadian universities vary, this seems specifically used also in Quebec:

"Graduation WITH DISTINCTION
Students in degree programs who have achieved an overall average of 80% and no grade lower than 70% on the entire program with no failed courses will graduate “with distinction.”
Notes:
Students who qualify for Graduation “With Distinction” will receive the designation on diplomas, transcripts and reports."
https://www.uwo.ca/arts/counselling/awards/distinction.html

Also, the 4.3 mark does also seem to be top level, so I think this would work.
This Wikipedia describes the numeric grading levels worldwide, covering Canada, with a section on Quebec.
https://en.wikipedia.org/wiki/Grading_systems_by_country#Que...


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Note added at 5 hrs (2022-11-15 17:43:02 GMT)
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This is a Canadian source term, which is the way I would translate this. I have used Canadian translations, rather than Australian variations because Canada is a bi-lingual country, and these terms will be understood within a Canadian context. But literal equivalents cannot be assumed unless the source institution were to make specific reference to it IMO.

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Note added at 5 hrs (2022-11-15 17:44:27 GMT)
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What I mean is that I would stick to terms that have been used by Canadian graduates and institutions, given that this is a bi-lingual country anyway.

I think you should use a literal translation rather than trying to shoehorn it into some kind of English-language equivalent.

In Steve's reference, the next grade down from "excellence" is "très bon", so it seems logical to translate it as "excellent".