What makes some characters better or worse online? [closed]

When people talk about this sort of thing, what they generally are referring to is two things:

1. The ease of perform that character's combos online. Characters that have very timing-dependent combos (1-frame links, etc) will generally be harder to play online than offline in most circumstances. This is due to the way that an online match's cadence can occasionally slow down or skip around due to latency fluctuations.

2. The ease of reacting to (and countering) that character's moves online. Due to the latency involved in online play, player input can sometimes be delayed to a sufficient extent that things that would normally be counterable "on reaction" become much more difficult to counter online. (This is also what people are referring to when they say a particular strategy "only works online.") In particular, moves that start up very quickly, cover a large distance, have startup invincibility, or have a short recovery time are often used frequently online by players who are looking for easy online wins.

   For example, Dudley's Machine Gun Blow (especially the EX version) will move him a very large distance across the screen very quickly; while it's entirely possible to see it coming and block in an offline match, the slight input delay introduced in a typical online match can be enough to make it much more difficult to block in time.