Amounts in the Pre-RingCT era
For the Pre-RingCT version, verifying if the transaction amounts match, i.e. inputs=outputs+fee, is trivial as it is in bitcoin as the values are not hidden.
You will find below a graph where the inputs - outputs $>$ 1 XMR. You can also refer to the Resources section and use the Python codes to scan the blockchain and verify yourself that the amounts for every transaction match.
Highest amount transacted
The two biggest transactions in the blockchain happened at block heights: 131942 and 571428 with amounts of 506510.890000 XMR and 505499.870000 XMR respectively. If these transactions do not come from the same person then there are 2 persons that control more than 5% of the supply if they did not spend these XMR yet.