Why this script it's not doing damage to NPC/Bosses ?

It's probably because you're connecting the event after it was destroyed. Also, to check if a character is an NPC, you can use Players:GetPlayerFromCharacter() and if it returns nil it's not a real player.

script.Parent.OnServerEvent:Connect(function(plr)
    local Players = game:GetService("Players")
    local TweenService = game:GetService("TweenService")
    local Bls = game.ReplicatedStorage.BlasterSoul.Head:Clone()
    Bls.Parent = workspace
    Bls.boomer.Touched:Connect(function(hit)
        local hum = hit.Parent:FindFirstChildOfClass("Humanoid")
        local playerNPC = Players:GetPlayerFromCharacter(hit.Parent)
        if (hum ~= nil) and (playerNPC == nil) then
            hum:TakeDamage(1)
        end
    end)
    Bls.CanCollide = false
    Bls.Anchored = false
    Bls:PivotTo(plr.Character.HumanoidRootPart:GetPivot() * CFrame.new(0,1,-5) * CFrame.Angles(math.rad(37), 0, 0))
    task.wait()
    Bls.Anchored = true
    local CHARGING = TweenService:Create(Bls.Charging, TweenInfo.new(2,Enum.EasingStyle.Linear), {Transparency = 0, Size = Vector3.new(2,2,2)})
    CHARGING:Play()
    CHARGING.Completed:Wait()
    Bls.boomer.Transparency = 0.5
    local Beam1 = TweenService:Create(Bls.boomer, TweenInfo.new(1,Enum.EasingStyle.Linear), {Transparency = 0.5, Size = Vector3.new(130.864, 2.4, 2.8)})
    Beam1:Play()
    Beam1.Completed:Wait()
    Bls.Charging:Destroy()
    Bls.boomer.Beam1.Enabled = true
    Bls.boomer.Beam2.Enabled = true
    Bls.boomer.Beam3.Enabled = true
    local Beam2 = TweenService:Create(Bls.boomer, TweenInfo.new(0.2,Enum.EasingStyle.Linear,Enum.EasingDirection.Out,19, true), {Size = Vector3.new(130.864, 3.2, 3.2)})
    Beam2:Play()
    Beam2.Completed:Wait()
    Bls.boomer.Beam1.Enabled = false
    Bls.boomer.Beam2.Enabled = false
    Bls.boomer.Beam3.Enabled = false
    local Beam3 = TweenService:Create(Bls.boomer, TweenInfo.new(2,Enum.EasingStyle.Linear), {Transparency = 1, Size = Vector3.new(130.864, 0.001, 0.001)})
    Beam3:Play()
    Beam3.Completed:Wait()
    Bls.boomer:Destroy()
    local AdiosHead = TweenService:Create(Bls, TweenInfo.new(2,Enum.EasingStyle.Linear), {Transparency = 1, Position = Bls.Position + Vector3.new(0,10,0)})
    local AdiosEye1 = TweenService:Create(Bls.LeftEye, TweenInfo.new(2,Enum.EasingStyle.Linear), {Transparency = 1, Position = Bls.LeftEye.Position + Vector3.new(0,10,0)})
    local AdiosEye2 = TweenService:Create(Bls.RightEye, TweenInfo.new(2,Enum.EasingStyle.Linear), {Transparency = 1, Position = Bls.RightEye.Position + Vector3.new(0,10,0)})
    local AdiosJaws1 = TweenService:Create(Bls.Jaws.rja, TweenInfo.new(2,Enum.EasingStyle.Linear), {Transparency = 1, Position = Bls.Jaws.rja.Position + Vector3.new(0,10,0)})
    local AdiosJaws2 = TweenService:Create(Bls.Jaws.LJA, TweenInfo.new(2,Enum.EasingStyle.Linear), {Transparency = 1, Position = Bls.Jaws.LJA.Position + Vector3.new(0,10,0)})
    local AdiosUnion = TweenService:Create(Bls.Union, TweenInfo.new(2,Enum.EasingStyle.Linear), {Transparency = 1, Position = Bls.Union.Position + Vector3.new(0,10,0)})
    local AdiosInside = TweenService:Create(Bls.Inside2, TweenInfo.new(2,Enum.EasingStyle.Linear), {Transparency = 1, Position = Bls.Inside2.Position + Vector3.new(0,10,0)})
    AdiosHead:Play()
    AdiosEye1:Play()    
    AdiosEye2:Play()
    AdiosJaws1:Play()
    AdiosJaws2:Play()
    AdiosUnion:Play()
    AdiosInside:Play()
    Bls:Destroy()
end)