Credit Suisse said 16 billion Swiss francs ($17.24 billion) of its Additional Tier 1 debt will be written down to zero on the orders of the Swiss regulator as part of its rescue merger with UBS, angering bondholders on Sunday. FINMA, the Swiss regulator, said the decision would bolster the bank's capital. The move reflects authorities' desire to see private investors share the pain from Credit Suisse's troubles.