This is a simple but effective upgrade for any X-men ally that wants to attack. Consider a 2-ATK ally. Attack Training grants 2 extra 3 damage attacks plus 1 extra damage per starting hit point for 2 resources, so likely around 8 or 9 damage...amazing value. You need to actually use all those hit points, or else this is no better than Sidearm, but the added damage over time is impressive. This combos particularly well with certain X-Men allies like Wolverine, whose self-heal grants you more uses of the ATK bump, and Dust, who wants to sweep away several minions at once with a large ATK stat.