I have been reviewing a lot of my old Japanese lessons as of late and I find that I keep thinking there were words used to express gratitude beyond a simple thank you. I recall ありがとう and the more polite どうもありがとうございます/した. But I keep wondering. When trying to express deep gratitude to someone in Japanese, are there any other words or way to say it? Adding たくさん to it just doesn't sound right to me.