I appreciate the post, but I don't think it's constructive to argue that the Gwangju Uprising was bloodier than June 4. That's only true if you go by official numbers put out by the CCP.
To give a starting point to the discussion; the English Wikipedia gives about the same summary for the independent estimates of casualties related to both events: from hundreds to thousands.
https://en.wikipedia.org/wiki/Gwangju_Uprising
https://en.wikipedia.org/wiki/1989_Tiananmen_Square_protests
Victims have a hard time coming forward if there is a strong possibility of being victimised again (korea has a long history of blacklisting victims families for generations, it's not just a north korean thing).
Also it doesn't mean anything. If you're saying the numbers we have might be wrong, that is an useless statement for the purpose of comparing the two incidents.