From Vitruvius’s Triad, I think stability/Firmitas is the most important. Without stability the building cannot withstand loading present in the structure and will lead to failure, causing harm to people inside. Utility/Utilitas is the second most important triad because even if the architecture is aesthetically pleasing, there is no point if the architecture lacks any uses or purpose for the public. While the beauty/Venustis should be considered, it does not triumph over structural integrity or utility.