Light and Darkness Dragon

If(somehow) I have a LADD with 300 Attack and a spell trap/effect is activated, does LADD still negate it?

the effect still activates automaticly, but it will resolve without effect. The same thing applies with a propper attack but with a def lower than 500.

so effect activates but fizzles without high enough attack?

yes, it resolves without doing anything. But that is a great way to ensure, that an effect goes through. For example you could activate mirror force while there is a weak LaDD and your opponent can't use Stardust/Seven Tools against it because the next chain link is LaDD.

"The effect "When a Spell or Trap Card is activated, or the effect of an Effect Monster is activated, that activation is negated and this card loses 500 ATK and DEF." of "Light and Darkness Dragon" is a Quick Effect. The effect can only be activated in Chain to the activation of a Spell, a Trap or and Effect Monster's effect. Furthermore, decreasing its ATK and DEF by 500 occurs when activation-negating effect resolves"

if you don't have 500 atk and def to give up then the negation eff cant resolve.

the effect can only be activated 4 times without a bonus of def, and is activated with your effects also

got it

thanks gais