Kirby & the Amazing Mirror
The first he is encountered when he slashes Kirby into four different colored Kirbies. Dark Meta is then seen defeating Meta Knight and sealing him within the Dimension Mirror, shattering it to prevent Kirby from being able to reach him. The second time he appears he he is disguised as Meta Knight and fights Kirby. Once he is defeated he retreats. The third and final time he is fought is within the Dimension Mirror. He again attempted to disguise himself as Meta Knight to fool Kirby, but the real Meta Knight reveals the impostor. Dark Meta Knight then assumes his true colors and fights Kirby. When he is finally defeated his body shatters and a portal opens up leading to the true mastermind, Dark Mind.
Kirby: Triple Deluxe
Although Dark Meta Knight does not appear in person until Dedede Tour has been unlocked, it is strongly implied that he is the true main antagonist of the entire game (instead of Queen Sectonia), as he was in control of the Dimension Mirror the entire time, which had slowly corrupted Sectonia into evil and caused her to send Taranza to capture the lower world's hero.
He appears in this game as the hidden true main antagonist and final boss of Dedede Tour. After the defeat of Shadow Dedede, King Dedede traveled into the Dimension Mirror and encounters Dark Meta, who is now far more powerful than before, no longer working for Dark Mind, and is in full control of the Dimension Mirror. Dark Meta was considerably more powerful in his reappearance, being able create clones of himself and dispense mach tornado's freely. Once he is defeated, he is sealed within the Dimension Mirror, which King Dedede then smashes.
He also appears as the penultimate foe in The True Arena. Upon Kirby destroying him a second time, he violently shatters like glass, leaving Kirby to destroy Sectonia Soul (who is still under Dark Meta Knight's evil power and influence, although his physical body is destroyed) however, as Dark Meta Knight had been destroyed before in the same way by Kirby, it is likely that he will make a return.