“Legendary Flame Lord” gets Spell Counters when Spell Cards resolve, not when they are activated.
If you activate a Spell Card, and your opponent chains “Call of the Haunted” to Special Summon “Legendary Flame Lord”, “Legendary Flame Lord” does not get a Spell Counter for that Spell Card because “Legendary Flame Lord” must be face-up on the field when the Spell Card is activated and when it resolves in order to get a Spell Counter.