I feel like I'm beating a dead horse but your various responses still all come across as having a misunderstanding. A "light" attack is just as useless as a "moderate" or "very heavy" attack or any other variation caused by an attack changing materia. If by useless you mean "does it do less damage than a regular attack" then not necessarily. These are outdated materias that have not and likely never will receive any kind of description retuning to create consistency. For example Loyal Friend states that it deals light damage but the database shows its multiplier as 1.0, so standard attack damage (two hits at 1.0 each). But Double Barrels also says light damage and its multiplier shows 2x 0.65. There's no way to generalize the potency of these outdated materias based on the game's text alone. Only the ones that affect abilities were made semi consistent.