I've a question about the situation in that duel. I owned red eyes slash dragon equipped with 2 cards, but my opponent destroyed my equip card & I wasn't asked if i'd like to negate the effect that destroyed my card
Don't play any other game, play Yu-Gi-Oh!, don't play games from multinational corporations.
Either your opponent effect didn't target, OR it missed timing since negate effect is "when" not "if".
Did you take down the replay? It won't load.
I haven't watched the replay, but I think there are 2 possibilities:
1. The destruction effect your opponent activated didn't "target", as Slash Dragon can only negate effect that "target"
2. Slash Dragon's effect "missed the timing"