onerous (adj) - involving a great deal of difficulty, effort, or obligation; burdensome [oh-ner-uhs]
BREAKDOWN: ONER- (burden) + -OUS (full of)
an onus is a duty, responsibility, or burden
“Taxation according to income is the most effective instrument yet devised to obtain just contribution from those best able to bear it and to avoid placing onerous burdens upon the mass of our people.” —Franklin D. Roosevelt