even-tempered
US /ˌiːvənˈtempərd/
UK /ˌiːvənˈtempərd/

1.
not easily annoyed or upset; calm and steady
:
•
She's known for being very even-tempered, rarely getting angry.
•
An even-tempered leader can handle crises calmly.
not easily annoyed or upset; calm and steady