There are many events are available in Native Magento 2 but some of the difficult events of cancel action of payment, invoice or order are as below,
1. order_cancel_after
This event is used after order canceled. If you want to do something after an order is canceled you can use this event.
Check file, vendor/magento/module-sales/Model/Order.php at cancel() function.
$this->_eventManager->dispatch('order_cancel_after', ['order' => $this]);
2. sales_order_invoice_cancel
Allows you to cancel the order invoice when you canceled the order.
Check event called at, file, vendor/magento/module-sales/Model/Order/Invoice.php at cancel() function.
$this->_eventManager->dispatch('sales_order_invoice_cancel', [$this->_eventObject => $this]);
3. sales_order_payment_cancel_invoice
Allows you to cancel the order invoice when you canceled the order.
Check event called at, file, vendor/magento/module-sales/Model/Order/Invoice.php at cancel() function.
$this->_eventManager->dispatch('sales_order_invoice_cancel', [$this->_eventObject => $this]);
4. sales_order_payment_cancel_creditmemo
Event defined under vendor/magento/module-sales/Model/Order/Payment.php using cancelCreditmemo() function but this function is not called at any file. Might be used in future developments. This event contains payment and specified creditmemo object.
$this->_eventManager->dispatch( 'sales_order_payment_cancel_creditmemo', ['payment' => $this, 'creditmemo' => $creditmemo] );
5.sales_order_payment_cancel_invoice
Cancel specified invoice from order and update self-total from order invoice.
Event defined under vendor/magento/module-sales/Model/Order/Payment.php
$this->_eventManager->dispatch( 'sales_order_payment_cancel_invoice', ['payment' => $this, 'invoice' => $invoice] );
This event contains payment and invoice object.
6. sales_order_creditmemo_cancel
When you want to refund from a specific order or specific item from order,
Your best suitable event is, sales_order_creditmemo_cancel
$this->eventManager->dispatch('sales_order_creditmemo_cancel', ['creditmemo' => $creditmemo]);