Gliders are stressed to very high g values (a modern composite aerobatic category glider would be designed for routine operation up to 7g, and the actual structure for 2.25x that, so just under 16g.
But, I doubt that you'll find any glider with the control authority to reach those sort of values - glider aerobatics doesn't generally exceed around 4g, the extra margins are really to handle the operating environment - low wing loading / high aspect ratio, with manoeuvring and gust loads.
Conversely a modern fighter is probably designed to 9g, plus a 1.5 safety factor (maybe higher for a plastic ship like Eurofighter), so that would be around 13.5g - the difference is that it's got the control authority (and good reason) to go up to 9g and operate routinely.
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