Remember Slade Wilson a.k.a Deathstroke? Well, the first main villain of the series will make his comeback and things will get very ugly as explained by the producers.
Deathstroke And Green Arrow
The hatred between Slade Wilson and Oliver Queen started during the pilot series of Arrow. Slade Wilson was once a good friend of Oliver Queen but due to immense differences, their friendship ended. Deathstroke mentored Green Arrow and taught everything he needs to know about survival and combat. Slade Wilson was injected with mirakuru serum after a near-fatal accident. As show oin Season 1, the injection of mirakuru serum didn't do no good to Slade. He turned evil and deadly. He was on a path of destruction and seeks vengeance against Anthony Ivo who killed Shado.
But his vengeance didn't stop there. When Slade Wilson found out that Oliver was one of the reason why Shado died, he looked for Oliver Queen and wants to suffer the same fate as Shado did. If you recall the episode where Oliver was asked on who should be saved, either Sara or Shado, then you will understand why Slade Wilson is angry towards Oliver Queen. They battled aboard the Amazo and Oliver had the upper hand, he was able to poke/stab the right eye of Slade Wilson. He taught he killed Slade Wilson but after half a decade, Slade Wilson returned, and is now known as "Deathstroke".
Deathstroke is somehow successful with regards to avenging the death of Shado. He was able to kill people who are close to Oliver Queen, especially when he ended the life of Oliver's mother. Deathstroke or Slade Wilson was not contented with the misery he brought to Oliver. Day in and day out, he is looking ways to permanently eradicate Oliver Queen. He also stalked the Green Arrow's sister which triggered Oliver to do some action.
Deathstroke's Return Confirmed
The 100th episode of the massive series will be special to say the least. Not only Deathstroke's return was confirmed but, Green Arrow will be in a unfamiliar territory. The synopsis as reported states that Oliver Queen(Green Arrow) will wake up in an alternate reality where The Queen's Gambit was involved. The season opener will also show that his parents, Moira and Robert Queen( Susanna Thompson and Jamey Sheridan) are actually alive. This scenario will lead Green Arrow to question his existence and the reality he is in.
"It is such a radical departure from anything that we have ever done on the show," star Stephen Amell attested during TVLine's visit to the show's Vancouver set. "We utilize the fantastical elements that we bring in on The Flash and carry through to Legends of Tomorrow with the present-day storyline to create something... that is not a flashback [or] a flash-forward. It's something else entirely." As per Stephen Amell,the unique scenario "basically gives us license to do whatever we want and to show some things that we'll never be able to show, to have some characters interact that will never be able to interact on the show again - probably."