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An issue can only have one assignee, so I am taking a guess that when you say "all the assignee for an issue", you mean you want to see all the people who have been assigned to it, now and in the past.
In Scriptrunner, https://library.adaptavist.com/entity/show-assignee-history actually gives you it in a panel on the issue screen. The main loop in the script is the bit you need.
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