user114111: I have Bitcoin-Core wallet.dat with a single address and a small amount of bitcoins in it.
Say I want to send all the available bitcoins I have, and then never use that wallet again. Can I use an online computer for that, including entering the passphrase while connected to the internet? Will anybody be able to steal any bitcoins from me?
Thanks

user13866: 
if my computer is infected and my passphrase is compromised, I'm going to do this transaction and never use that wallet again. Is there a risk that my transaction won't be fulfilled successfully?

Users of Electrum found to their cost that it is possible that a compromised computer contains a malicously modified wallet that shows it sends money where the user asked (and presumably shows the transaction as successful) but actually sends the money to the address of a thief.
If you suspect a computer may not be clean, you can't be certain that any bitcoin core wallet on that computer has not been compromised in some equally malicous way.
Quantifying the risk is hard, and deciding on an acceptable level of risk is a personal choice. However the risk is not zero.

114111: <p>I have Bitcoin-Core wallet.dat with a single address and a small amount of bitcoins in it.
Say I want to send all the available bitcoins I have, and then never use that wallet again. Can I use an online computer for that, including entering the passphrase while connected to the internet? Will anybody be able to steal any bitcoins from me?</p>
<p>Thanks</p>
 13866: <blockquote>
<p>if my computer is infected and my passphrase is compromised, I'm going to do this transaction and never use that wallet again. Is there a risk that my transaction won't be fulfilled successfully?</p>
</blockquote>
<p>Users of <a href="https://github.com/spesmilo/electrum/issues/4968" rel="nofollow noreferrer">Electrum</a> found to their cost that it is possible that a compromised computer contains a malicously modified wallet that <em>shows</em> it sends money where the user asked (and presumably shows the transaction as successful) but <em>actually sends</em> the money to the address of a thief.</p>
<p>If you suspect a computer may not be clean, you can't be certain that any bitcoin core wallet on that computer has not been compromised in some equally malicous way.</p>
<p>Quantifying the risk is hard, and deciding on an acceptable level of risk is a personal choice. However the risk is not zero.</p>
