Formal:
* Un excellent professeur: This is the most direct and formal way to say "a great teacher."
* Un professeur remarquable: This means "a remarkable teacher" and emphasizes the teacher's exceptional qualities.
Informal:
* Un super prof: This is a more casual way to say "a great teacher."
* Un prof génial: This means "a brilliant teacher" and is even more informal than "super prof."
Other options:
* Un bon professeur: This means "a good teacher" and is a more neutral way to describe a teacher.
* Un professeur formidable: This means "a formidable teacher" and emphasizes the teacher's strength and power.
* Un professeur inspirant: This means "an inspiring teacher" and highlights the teacher's ability to motivate students.
The best way to say "a great teacher" in French will depend on the context and the level of formality you want to use.