Example1:

The upgrade contains the following set of cpnflicting VIBs:
Mellanox_bootbank_net-mlx4-en_1.9.9.0-1OEM.550.0.0.1331820

VMware - vib conflict during ESXi upgradeCan’t upgrade esxi 5.5 to 6.0 due a vib conflict

So:

~ # esxcli software vib list|grep Mel
net-mlx4-en                    1.9.9.0-1OEM.550.0.0.1331820           Mellanox         VMwareCertified   2014-05-01

~ # esxcli software vib remove –vibname net-mlx4-en
Removal Result
   Message: The update completed successfully, but the system needs to be rebooted for the changes to be effective.
   Reboot Required: true
   VIBs Installed:
   VIBs Removed: Mellanox_bootbank_net-mlx4-en_1.9.9.0-1OEM.550.0.0.1331820
   VIBs Skipped:
~ # reboot

Example2:

The upgrade contains the following set of conflicting VIBs:
HUAWEI_bootbank_hio_2.0.0.42-1OEM.550.0.0.1331820

~ # esxcli software vib list | grep HUAWEI
~ # esxcli software vib remove -n hio
~ # reboot