Put up or shutup
In all seriousness, I started Aikido as a result of bullying. I've had to beg for my life once and even came close to dying, all without having done anything to deserve it. It was something I could never forget and I've always harboured a deep-seated hatred for bullies as a result.
Don't blend in, it doesn't work. You've already got the red dot on your forehead. That guy isn't going to stop until you either stop coming or take him out. Guys like him are insecure about themselves, and when confronted with their inadequacy, rather than work harder to compensate like the rest of us true budoka's, he starts to attack others, physically or emotionally. He is small minded and even smaller hearted and I do not consider him an Aikidoka.
Ignoring doesn't work either, I've tried all of the tricks and tips people give you. These guys never had any experience in this, and so they'll just give you some halfassed answer and leave it at that. Even if you become a fucking ninja and disappear from view, that jerk will hunt you down and put you down, just for his own satisfaction. Never give in and never back down, don't ignore and show him what you got.
There's usually only two ways to deal with guys like him (from my two years of experience in hell). Beat the living crap out of him till he's either half-dead or given up, and then tell him train instead of flap lips. Another way is to speak to your sensei about it and see if he can't convince the bully to follow Aikido's principle and improve himself.
This guy isn't doing as much as you to improve, and if he isn't as talented as you, then that should be a signal for him to work twice as hard to keep up. Frankly, he should be happy to have a rival now. For him to act in this way as a result of you improving just goes to show his shallowness. Usually, people like him have never experienced what it's like to be bullied around in their life, but have been wounded in some other way. However, that is not an excuse to harm others and continue the cycle of pain. Once he started to attack you verbally, he's a perp, and no longer the victim
In other words: you must confront. He will not stop, so neither should you. Show him that you will not stand being pushed around, even by a sempai, and that you are a true budoka and Aikidoka, unlike him.
P.S. I am not talented like my sempai's and even some kouhai's, so I put in twice the time they do, and it shows. My sempai's encouraged me though, and comes more regularly as a result to keep up their skills with me. Don't settle for any less, these are the kind of people that deserves to be called sempai!