You're a bloody teemo, a champion who is well known as being one of the squishiest champs in the game. The entire video took nearly 19 seconds of him to kill you. A time frame that is actually incredibly long, which was plenty of time for him to chase after you and finish you off, while he throws down at minimum four auto attacks.
So let's see you're playing a champion who is under leveled, a champion who is known for being incredibly squishy, and you were completely caught out, took both death mark, shadow slash and electricute, and you wonder why you die?
You made a unwise play and died for doing so.
So sick of people doing stupid shit and going "oh it's the champion that's broken, it had nothing to do with me"