yuris starve vemon is actually pretty broken
If this card is Fusion Summoned: You can make this card gain ATK equal to the ATK of 1 Special Summoned monster your opponent controls until the end of this turn. Once per turn: You can target 1 Level 5 or higher monster your opponent controls; until the end of this turn, this card's name becomes that monster's, and replace this effect with that monster's original effects. If this Fusion Summoned card is destroyed: You can destroy all Special Summoned monsters your opponent controls.
which basicly means it can beat the egyptian god cards and the sacred beasts by getting attack equal to there power, beats don thousands numeronia, gains effects from cards like neo galaxy eyes photon dragon and shooting quasar dragon it could gain the effect of 5 god dragon and its power
and not to mention starve venom can easily be summoned
and in the anime it was able to defeat 5 fusion monsters at once
oh and the effect of copying an opponents ability it can basicly gain even yubels power which means you attack youbel yubel activates its effect then you use starve venoms effect to copy yubels effect and reflect the reflecting move right back
heck it can even counter dark requiem xyz dragon by gaining its attack points then copying dark requiems effect thus reducing requiems attack to zero and gaining attack equal to dark requiems which is 3000
so 3000 + 3000 +2800= 8800 attack for a one turn kill since dark requiem would have 0 attack points