It takes quadruple damage from rock-type moves being that Scyther is a Bug/Flying type, but it's super fast. It's also weak against Ice-types, Fire-types, Flying-types, and Electric-types. With that many weaknesses, it wouldn't be a good Pokemon.

Yeah Scyther is pretty good.

It is if you train it the right way.But to be fair, there are lots of pokemon that aren't good choices to start off with like Sandslash due to its weakness to grass, fightning, water, steel,and ice types. Other pokemon I wouldn't advise starting out with are Hitmonlee due to its weakness against flying and psychic types, Kangaskhan due to its weakness against fightning types and Flareon due to its weakness against ground and water types.While yes there are other elements theyr'e strong against like Sandslash is strong against fire, flying and electric types, Hitmonlee is strong against dark, normal, rock and ground types, theyr'e pokemon I would wait until down the line to catch.

depending on what you mean by "good"

Scyther can really cut your opponents down to size.

^^