Megadosing B6 can lead to B6 toxicity/syndrome as a result of its longer half life and ability to accumulate in the system. Between multivitamins, energy drinks, preworkouts and food, it's very easy to go well above the recommended amount. I'm currently recovering from B6 induced peripheral neuropathy (tingling in my feet) caused by 20-50mg/day over several years.
https://en.wikipedia.org/wiki/Megavitamin-B6_syndrome