Did you read the "Necrosha" or "Second Coming" issues featuring Cypher? I guess not, 'cause otherwise you'd certainly not put him among the weakest X-Men. Even though one might assume so at first look on his powers, he actually kicked major a*s (that of the New Mutants, some future humans and that of "Bastion's Mastermold").
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THE CORPS IS MOTHER
THE CORPS IS FATHER
actually i have read both nercosha and second comeing i was not really that impressed with him i found them out of charcter with his previous showings and i am generally dissapointed that he got ressurected when other similar charcters are being ignored when did prodigy last get any cover time ? also the xmen have alot of trained martial artisits allready wolverine phylocke shadowcat sage alot o people forget that cyclops has a good level of Judo.. i personaly feel he has become alittle too similar to Karnak however i do admit that perhaps he is not as weak as some other xmen hanging around utopia
but at least he had some powers, like swam relal fast, breath under water ect. What about blue boy, or what ever he calls. Who was a black guy who mutation was the he turned blue......that was it.
There is probably a large tie for weakest mutants really. Throughout the comics, there are multitudes of nameless mutants with seemingly aesthetic or otherwise "weak" mutations. i.e. being blue/green/yellow, multiple eyes, a long neck.