Unforgiving terrain: The GR20's unforgiving terrain, with steep climbs, rocky paths, and treacherous descents, is certainly challenging. However, other hiking trails in Europe, such as the Tour du Mont Blanc or the Haute Route, also offer challenging terrain. While the GR20 may be more intense, it's not necessarily the toughest.

Unpredictable weather: It's unpredictable and dangerous weather, with frequent storms and snowfall, is indeed a challenge that hikers must be prepared for. But again, other mountainous regions in Europe can also experience harsh weather conditions. The weather on the GR20 may be more extreme, but it's not uniquely so.

Lack of amenities: It's lack of infrastructure, including limited accommodations and supplies, can indeed make the trek more challenging. However, this is also true for other remote hiking trails in Europe, such as the Laugavegur trail in Iceland or the Tatra Mountains in Poland. The GR20 may have fewer resources, but it's not the only trail that requires careful planning.

Physical demands: It's physically demanding terrain requires a high level of physical fitness, endurance, and agility. However, other long-distance hiking trails, such as the Camino de Santiago or the Appalachian Trail, also demand a high level of physical fitness. While the GR20 may be more physically demanding, it's not the only trail that requires a high level of athleticism.

Mental toughness: Challenging terrain and unpredictable weather conditions can require a high level of mental toughness. However, other hiking trails can also be mentally demanding, such as the John Muir Trail in California or the West Highland Way in Scotland. The GR20 may be more mentally challenging, but it's not uniquely so.

So yeah, it is tough. Is it necessarily the toughest in Europe? Either way, good efforts on your side and to be taken seriously by anybody going for it!