This section provides information on the variation of character interpretations both pre-Crisis and in iterations since Crisis. Focus is on characters defined by their given name (Alan Scott, Jay Garrick, etc.) rather than code name (Green Lantern, Flash). Emphasis is on interpretations where the character had a major role versus a cameo or non-essential story role to minimize clutter.
The Golden Age Mr. Terrifc
The history of Mr. Terrific on Prior Earth-0 is thought to be largely similar to that of the original Earth-Two version, up to his death at the hands of the Spirit King on the Justice League satellite in the late 1970's. The primary differences would be interactions with Golden Age versions of Superman, Batman and other characters who did not exist in the Earth-0 timeline as they had in that of Earth-Two. He is revealed to have a degenerate brother Ned, who is the grandfather of the villainess know as Roulette. Whether these relationship exist on the original Earth-Two is not known. In this timeline, the final accounting of Mr. Terrific's murder was revealed. After returning to Earth-2, the JSA tracked the Spirit King, revealed to have become a pawn of Shaitan to Stonehenge while he was still in the in Flash's body. In the ensuing battle, The Spirit King assumed control of Doctor Fate and allowed the Flash to lure the Spectre to him. As Shaitan and Romaine held the Spectre at bay, the recently-deceased Sloane intervened and disrupted the connection between Romaine and Shaitan, casting the Spirit King into the depths of Hell. Mister Terrific had few seconds of corporeal existence to bid farewell to his JSA comrades and then went to his afterlife reward (The Spectre vol. 3. #54). Whether this version of events occurred on the original Earth-Two has not been revealed.
In the mid-1990s, The Spectre happened up a young man named Michael Holt considering suicide after a series of personal reversals. To inspire the man not to give up on life, the Spectre recounted the life story of Terry Sloane and his life as a costumed in adventure. Holt not only decided to live, he took up the mantle of Mr. Terrific himself (The Spectre vol.3 #54). He ultimately became a member of a re-formed Justice Society and served in that role until the history of Prior Earth 0 was erased in the Flash point event.
The Terry Sloan of the revised Earth-2 shares the extensive acumen in multiple disciplines of the original Earth-Two version and goes by the codename Mister o8. He has, however, of a Machiavellian bent and when the forces of Apokolips attacked Earth, destroyed afflicted areas with no thought for civilian life. He is widely regarded as one of the worst villains in the history of Earth-2. (Earth-2 #1). He survived the destruction of his home world but was killed in the early days of the new society formed by the survivors (Earth 2: Society #3)
The history of Mr. Terrific up until the late 1940's on Earth-22 is largely identical to the history on Earth-0. He retired at the end of World War II and expanded his industrial holdings, though reporter John Chambers (Johnny Quick) questioned the scruples employed. He was present at the cataclysmic battle in DC against Dyna-Man and the Ultra-Humanite and is not a known casualty (The Golden Age LS).. Years later, an unrelated person besmirched the legacy of Mr. Terrific by becoming Mr. Terrific II, an otherwise untalented but heavily armed individual with little understanding of "Fair Play". (Kingdom Come LS).
The Terry Sloan is a former field agent for military intelligence on vacation with his fiancée in Switzerland when she is killed in a struggle with The Scarecrow, a Nazi "cleaner". Sloan adopts the identity of "Mr. Terrific" and joins Batman's team grudgingly. When the war ends, Sloane abandons the costumed life and begins running a series of companies, including a pharmaceutical firm study the powers of Superman. When Superman is revealed to be the rogue Kryptonian Zod, Sloane perfects a formula to allow Batman to defeat Zod in hand to hand combat. He later reforms the group with Batman at Mr. Terrific. His ultimate fate is unknown. (JSA: The Liberty Files LS I and II).