How to defeat Stalker solo?
If solo, I can only face him in melee with Valkyr (lvl 24), but somehow Stalker cancels Valkyr's Hysteria ability (making me vulnerable to attacks again).
I didn't try with the Cernos Bow: I wonder, if I hit him in the head will I instagib him or at least do massive damage (like 40% of his bar)?
If not, are there any other efficient ways?
Solution 1:
I will give a rule list for how to defeat Stalker.
Use high damage weapons. The stalker has a lot of health and armor, so if you can't deal enough damage to him, he will not die.
Do not, and I repeat, DO NOT use any buffs. The Stalker can "Dispel" any buff instantly, instantly removing them and any effects they cause (Trinitys Blessing still restores HP, but he will dispel the damage resistance) making them an effective waste of your energy.
Do not stop moving at any point. If you stand still too long he will destroy you. Using a bow or sniper (besides rule #4) can lower your movement speed while trying to aim. This will give him an easier target.
Do not use hard to aim weapons. Because the fact that the Stalker is highly mobile, trying to use a sniper or a bow can make it impossible to hit him. A weapon like Soma, Boltor Prime, or Penta is recommended.
Solo is usually a no-go (see what I did there). Even if you do not want to, you should be playing with other players. Other players can deal more damage, possibly heal, and even extend the fight if you die (if another player is marked, he will move to kill the next target, and the next (if there is another)). This can allow you to revive and continue fighting (but if the next player who he is chasing dies (and there is no one else to chase), he will start his escape phase).
Stalker is immune to a lot of movement impairing effects, like Rhino's Stomp ( he will not be stunned, but will take some damage).
Do not be stupid. Use logic to defeat him. Examples: If he is using absorb, don't attack him (use this time to get away, and scavenge resources). If he is about to Slash Dash, get out of his way. Ect.
If you see him spawning, do not hesatitate to destroy him. My friends and I have killed him many times before he even had the chance to stand up.
Extra note on #2 on this list. Last time I played, Stalker had an ability (not passive) to dispel moves, so it did take a bit of his time. A skilled team might be able to lock him into using despel over and over, making the fight verus a potato and not the Stalker. Can't be 100% sure on this one though, as I will need to do some quick research. Well, it seems he can be forced to stop for a bit (Dispel Wiki), around enough time to use one dispel. I don't know if you can fully turn him into a potato, but you can use it to get him to stop for a bit and beat him up.
Solution 2:
I like to use guns that can stun lock him. For example, the last time I solo'd Stalker, I was using the Zephyr frame, while using a Karak with high fire rate and Blast Damage to "stagger" him, so to speak.
I find that some good efficient ways to kill the Stalker solo revolve around using high damage output guns. Melee generally doesn't work, because the Stalker can easily shred through your armor. Guns like the Soma and the Boltor Prime work wonders and can easily destroy Stalker.