Who is Sonic exe worst enemy?

I'm curious, who do you consider to be Sonic exe's worst enemy? Is it a particular character from the Sonic the Hedgehog universe, or perhaps a foe that originates from outside the franchise? Is there a specific reason why this enemy stands out as Sonic exe's greatest challenge, whether it's due to their powers, tactics, or personal grudge? Share your thoughts on who you believe poses the greatest threat to Sonic exe and why.