If the trigger is generally academic challenge, it is possible that your son may enjoy learning from other resources, or another approach.

HALT is an acronym for common triggers for negative behavior or tantrums: Hungry, Angry, Lonely, Tired. Other threads have mentioned the effects of diet on moods.

If your son states things in a hurtful way, possibly the resources regarding Perspective Taking, Theory of Mind, Social Thinking would help him to be cognizant of the feelings of others.

You may have read this elsewhere on the forums...

Perfectionistic tendencies may be a sign of developing a fixed mindset rather than a growth mindset. One aspect or application is that gifted kids may stop taking appropriate risks in order to always be "right" or always be "smart" or never be "wrong", and this may work against them. The concept is nicely summarized in these youtube videos:
Ashley Merryman & Po Bronson: The Myth of Praise (link-
)
Teaching a Growth Mindset (link-
)

Parents may wish to read the book Mindset by Carol Dweck for tips on promoting a growth mindset.

A book which seems to understand perfectionism very well and which many find supportive is What To Do When Good Enough Isn't Good Enough. Another book you might like is Perfectionism: What's Bad About Being Too Good. While insightful, these are written gently for kids, in a style that is fun and engaging. With any of these books it may be wise for a parent to pre-read and decide if it seems to be a helpful tool to use in guiding their child.

Procrastination can be closely related to perfectionism.

A child considering "worst case scenario" and finding various work-arounds to keep moving forward may in some cases help reduce anxiety and add an element of self-confidence, even a sense of looking forward to taking on the challenge.

Two more books which come to mind:
- The Explosive Child
- Living with Intensity