Cheat Engine

[bird123]

yo
is it possible to hack yu gi oh??
they got no defense and very easy to get into game with it

[Dark Byte]

depends on the game.
In the VERY unlikely event that is uses your client to find out what cards you get, try the unrandomizer.

Of course, since it's online, high chance there's not much you can do. At most peek at stuff that is usually invisible or hidden

[Twilly]

It's possible. That's what I can tell you. I have seen people done it before.