L2TP: The most notable characteristic of L2TP is its inability to operate alone. To offer encryption or protection for data in transit, it must be paired with IPSec.
IKEv2: IKEv2 operates as a true protocol and controls the ipsec key exchange.
L2TP does include IPsec as a part of the VPN but it is a legacy protocol. IKEv2 is the newer one and is not yet available on the standalone devices. I hope it will help you.

L2TP is a VPN tunnel...
IKEv2 is a protocol used to setup a security association in the IPsec protocol...
IPsec is a security protocol used to authenticate and encrypt packets between two hosts...