One easy answer is any evasive 3-power creature, and you could count Davros, Dalek Creator
For example, if you attack with Incinerator of the Guilty and deal combat damage with it, use its triggered ability to deal damage, and then use Hard-Hitting Question to have it deal damage to another creature, it's still just one source even though it dealt damage three times during the turn
Rakdos is one of the weakest archetypes in the set, so that hasnt helped the mechanic much
Razorman Masticore will not deal damage again in the next combat step
In red, this is quite strong
Also, it is the only battle card so far that has flash, which increases its technical playability despite its casting cost compared to its maximum target size (only one, and only creatures)