Making this cost just double green doesnt sound totally implausible, and even if it only costs 5 or 6, its still a very strong play
In the case of Thanos, the Mad Titan, you can pay WUBRG to gain two +1/+1 counters before destroying all other creatures with an odd or even mana value, a decision you declare when activating the ability
Turning this around though you are more likely to play cheap low power spells in a deck if they have flashback and may be used for extra value again later
In addition to blanking Infernal Grasp, you can use it to save yourself from a scenario where theres no good blocks, or hold it to back up your go-wide flunge
Next come two obvious questions
[FOIL] Counterspell From Judge Gift Program Promo Card details Instant Rare Counter target spell