If a card in your graveyard is an artifact creature card, count it only once when determining how many Insect tokens to create for Aatchik’s first ability.

If Aatchik is dealt lethal damage at the same time as another Insect you control, Aatchik’s last ability will still trigger, causing each opponent to lose 1 life, but Aatchik won’t get a +1/+1 counter in time to save it.