Who would you kill?
I'd probably go for Glenn Leopold.
Walt Disney
That!
W̷̢̑͑͘ȩ̵́ ̸͔̥̉̐́t̴̺̲̭̒h̸͔̬͚̉͆i̵̺͙̥̿̽̑͝ǹ̵̮͓k̵̳̝̽͛.̶̭̍̏̽̃͜.̷̫͔̈̈́͠.̵̺͎̙̒͛ ̶̥̩̩̣͊͗̑M̴̝̓͐a̴̧̟̻͓͛̅ṯ̷̼̄̈͛ț̷̪̫̀ ̵̘͗̍W̶̦̯͛̍a̴̰̪̓̑r̵͚͉͆͌̋͠d̶̢̹͉̆͜.̴̪̅ ̶̡̈̋̄͜P̷̤̠̥̏͂͝r̷͎̱͎̻̈́̆̓̓e̸̮̫̥͛͐͠f̵͙̼̿̔ẻ̸̖͚r̸̛͍̀̈a̴̡̬̘̚b̴̟̻͛̏͗̆l̸͈̕ͅy̷̻̥̣̯̋ ̶̮͉̗̌́̋̍ͅt̴̨̮̞̅̉͜ŏ̸̠̪̪̕ ̶͓̣̃c̴̹̻̣̬̚͠o̴͉͗̋n̷͖͈̖̜̑s̴͓̤̏͛̆͘u̴̹̙̙̓m̶̙̬̃̽e̵̢̪̊͝ ̶̖̞̈́̐̀͘ͅh̴͎̘̒̅̓i̵͖̹̅͊̊m̵̱̔ ̶͕̑̕͝t̴̮̺̜̰̔̀̄h̸̙̻͖̑͐ö̴͖̺́̐̈ư̸̹̬̋g̵̞̳̞͌̽͗̈́ȟ̷̛̻͈͋̾͜,̵͔̬͓̥̽̉ ̶̳͈̭̓̎n̴̡͚͙͍̋ö̸̗͍̽͝ͅt̷͈͔̣̟̐̽͠ ̷̢̢̄͘ă̶͚̥̓̉ń̷̪͍̟́̚ ̵̡̆̉̄à̵̹̫̙͝s̷͖͚̈́͘͝ͅͅs̵̙̈́́͊̉a̵̡̡̜̋̄͋͑ͅs̵̲͍͙̭͋̍͛̒s̴͙̞͓̈͗i̵̠̹̻͔͗ṋ̸̈̽̽̽.̴̳̝̓̔ ̴̱́̋͐͘T̸͔̰͍̻̍͘h̸͖̻͑͘e̸̱̋ ̸̧͖̰̅͗h̷̟͇̙͛ų̴̬͉̓ň̴̢̟̥̜͝ǵ̷̱e̵͔͊̊r̷̨͖̓̅̍ ̷̢͎̦̉̆̏s̶̟͔̞̓͐t̷͍̪̲̖̂͗͠i̷̡̻̮̠̅̈́́̽l̶̬͔͕͐́l̵̛͇̥̲͙͊̔ ̴̦͓̊r̷̬͉̚e̵̠͈̠̔m̷͚͇̦͓̈̏à̶̤͓͍̓i̶̢̬̤̅́͝n̷̛̳̿͛̎s̴̼͚̲̹͐͑͘̚.̴͈̞̲͚̏́͝
̸̠̻̩̕
̴̛̼͉̰̹̅̕A̶̞͈̜̋̔͆͝n̶̫͇͇̰̽́̽y̶̯̺̪̾̒̐̕o̴̰͒͑͠n̸̮̻͊̀̿͜͝e̸̢͉͖̅̓͐̕ ̷̣̞̂̀̂͋ȅ̸̦̜͝l̸͎̈́̈̒s̸͕͙̍͛e̴̢̅̇ ̴̤͆̿ḥ̵̕͘ư̵̮̜̝̙n̸̼̫̏̓̋ͅg̴̯̘͑̔r̶̢̬̘̈́̋͜y̷̢͑͌͝ ̴̗̟̥͊̄͛ť̴͔̈̈́o̴̡̖͈̎d̵͈̰̽̍͊ͅą̵͈̎̓̅y̵̥̦̐̿̍?̴̘̉̾̄͒
Hitler before he kills Hitler.
Like... right before?
Would send the assassin back in the past to kill his great grandfather unknowingly just to see if it was possible.
I think it would end up not working, he would miss or fail, hence why he was able to exist since he never managed to kill his great grandfather in the past.
Or, he kills his grandfather, creating parallel universe where he never existed. However we can't visit because the machine was just designed to go back and forth in time, and not to jump dimensions. So, meh.
And the last theory is the lamest, but the coolest. He would vanish from timeline as soon as he succeeded and not get his payment. I would KeK really hard looking through the window, satisfied with my master plan.